Rill Theme

Instructions for developing a theme in Rill

Introduction

Themes are resources that define custom color palettes for dashboards in a Rill project. They allow you to customize the visual appearance of explore and canvas dashboards to match your brand or design preferences.

Themes are lightweight resources with no reconciliation cost. When a theme file is saved, Rill validates it but performs no heavy operations. Themes are referenced from rill.yaml for project-wide styling or directly from individual explore or canvas dashboards.

Core Concepts

Referencing themes

Themes can be applied in two ways:

1. Project-wide via rill.yaml:

# rill.yaml
explores:
  theme: brand
canvases:
  theme: brand

2. Per-dashboard in an explore or canvas file:

   # dashboards/sales.yaml
   type: explore
   metrics_view: sales_metrics
   theme: brand
   

Color formats

Themes support multiple color formats:

• Hex with # (recommended): "#FF6A00", "#6366f1"
• Hex without #: FF6A00 (works but less explicit)
• Named CSS colors: blue, plum, darkgreen, seagreen
• HSL values: hsl(180, 100%, 50%), hsl(236, 34%, 34%)

For consistency and clarity, we recommend using quoted hex values with the # prefix.

Recommended Theme Structure

The recommended approach uses separate light: and dark: blocks to define mode-specific colors. This ensures your dashboards look great in both light and dark modes.

# themes/brand.yaml
type: theme

# Light mode colors
light:
  # Core brand colors (required)
  primary: "#6366f1"     # Primary actions, emphasis, selected states
  secondary: "#8b5cf6"   # Secondary elements, supporting colors

  # UI surface colors (optional - defaults used if omitted)
  background: "#f8fafc"  # Page background
  surface: "#ffffff"     # Elevated surfaces, panels
  card: "#f1f5f9"        # Card backgrounds

  # KPI delta colors (optional - controls comparison/change value colors)
  # kpi-positive: "#16a34a"  # Green for positive deltas (defaults to gray)
  # kpi-negative: "#dc2626"  # Red for negative deltas (defaults to red)

  # Qualitative palette for categorical data (optional, 24 colors)
  # Used for bar charts, pie charts, legend colors by category
  color-qualitative-1: "#6366f1"   # Indigo
  color-qualitative-2: "#8b5cf6"   # Purple
  color-qualitative-3: "#ec4899"   # Pink
  color-qualitative-4: "#06b6d4"   # Cyan
  color-qualitative-5: "#10b981"   # Emerald
  color-qualitative-6: "#f59e0b"   # Amber
  color-qualitative-7: "#3b82f6"   # Blue
  color-qualitative-8: "#a855f7"   # Violet
  color-qualitative-9: "#ef4444"   # Red
  color-qualitative-10: "#14b8a6"  # Teal
  color-qualitative-11: "#84cc16"  # Lime
  color-qualitative-12: "#f97316"  # Orange
  color-qualitative-13: "#d946ef"  # Fuchsia
  color-qualitative-14: "#eab308"  # Yellow
  color-qualitative-15: "#0ea5e9"  # Sky
  color-qualitative-16: "#a855f7"  # Purple alt
  color-qualitative-17: "#22c55e"  # Green
  color-qualitative-18: "#fb923c"  # Orange alt
  color-qualitative-19: "#f43f5e"  # Rose
  color-qualitative-20: "#6366f1"  # Indigo alt
  color-qualitative-21: "#2dd4bf"  # Teal alt
  color-qualitative-22: "#facc15"  # Yellow alt
  color-qualitative-23: "#c084fc"  # Violet alt
  color-qualitative-24: "#4ade80"  # Green alt

  # Sequential palette for ordered data (optional, 9 colors)
  # Used for heatmaps, choropleth maps, intensity scales
  color-sequential-1: "#eef2ff"   # Lightest
  color-sequential-2: "#e0e7ff"
  color-sequential-3: "#c7d2fe"
  color-sequential-4: "#a5b4fc"
  color-sequential-5: "#818cf8"
  color-sequential-6: "#6366f1"
  color-sequential-7: "#4f46e5"
  color-sequential-8: "#4338ca"
  color-sequential-9: "#3730a3"   # Darkest

  # Diverging palette for data with a meaningful midpoint (optional, 11 colors)
  # Used for showing positive/negative deviation from a baseline
  color-diverging-1: "#dc2626"    # Negative extreme (red)
  color-diverging-2: "#f87171"
  color-diverging-3: "#fca5a5"
  color-diverging-4: "#fecaca"
  color-diverging-5: "#fee2e2"
  color-diverging-6: "#f3f4f6"    # Neutral midpoint
  color-diverging-7: "#dbeafe"
  color-diverging-8: "#93c5fd"
  color-diverging-9: "#60a5fa"
  color-diverging-10: "#3b82f6"
  color-diverging-11: "#2563eb"   # Positive extreme (blue)

# Dark mode colors
dark:
  # Core brand colors (brighter for visibility on dark backgrounds)
  primary: "#818cf8"
  secondary: "#a78bfa"

  # UI surface colors
  background: "#0f172a"  # Deep slate background
  surface: "#1e293b"     # Elevated surfaces
  card: "#334155"        # Card backgrounds

  # KPI delta colors (optional)
  # kpi-positive: "#4ade80"  # Green for positive deltas (brighter for dark mode)
  # kpi-negative: "#f87171"  # Red for negative deltas (brighter for dark mode)

  # Qualitative palette (adjusted for dark mode visibility)
  color-qualitative-1: "#818cf8"
  color-qualitative-2: "#a78bfa"
  color-qualitative-3: "#f472b6"
  color-qualitative-4: "#22d3ee"
  color-qualitative-5: "#34d399"
  color-qualitative-6: "#fbbf24"
  color-qualitative-7: "#60a5fa"
  color-qualitative-8: "#c084fc"
  color-qualitative-9: "#f87171"
  color-qualitative-10: "#2dd4bf"
  color-qualitative-11: "#a3e635"
  color-qualitative-12: "#fb923c"
  color-qualitative-13: "#e879f9"
  color-qualitative-14: "#facc15"
  color-qualitative-15: "#38bdf8"
  color-qualitative-16: "#c084fc"
  color-qualitative-17: "#4ade80"
  color-qualitative-18: "#fdba74"
  color-qualitative-19: "#fb7185"
  color-qualitative-20: "#818cf8"
  color-qualitative-21: "#5eead4"
  color-qualitative-22: "#fde047"
  color-qualitative-23: "#d8b4fe"
  color-qualitative-24: "#86efac"

  # Sequential palette (reversed for dark mode)
  color-sequential-1: "#312e81"   # Darkest
  color-sequential-2: "#3730a3"
  color-sequential-3: "#4338ca"
  color-sequential-4: "#4f46e5"
  color-sequential-5: "#6366f1"
  color-sequential-6: "#818cf8"
  color-sequential-7: "#a5b4fc"
  color-sequential-8: "#c7d2fe"
  color-sequential-9: "#e0e7ff"   # Lightest

  # Diverging palette (adjusted for dark backgrounds)
  color-diverging-1: "#ef4444"
  color-diverging-2: "#f87171"
  color-diverging-3: "#fca5a5"
  color-diverging-4: "#fecaca"
  color-diverging-5: "#fee2e2"
  color-diverging-6: "#475569"    # Neutral slate midpoint
  color-diverging-7: "#bfdbfe"
  color-diverging-8: "#93c5fd"
  color-diverging-9: "#60a5fa"
  color-diverging-10: "#3b82f6"
  color-diverging-11: "#2563eb"

Building an on-brand theme from a brand

A common request is "make a theme that matches <company>" or "build a theme that looks like <url>". Follow this process to produce a theme that emulates a brand while keeping dashboards legible.

Step 1: Extract the brand palette

From the brand's website or assets, identify a small structured palette before writing YAML. Prefer the brand's digital colors (from the live site / CSS) over print or PDF brand guidelines, since those are the colors users associate with the product on screen.

• Primary: the dominant brand color, usually the logo color or primary button color. This drives primary.
• Secondary / accent: a complementary or analogous color used for links or secondary actions. This drives secondary. If the brand is effectively monochrome, derive one by rotating the primary hue ~20–40° or using a desaturated variant.
• Background: whether surfaces are pure white, warm off-white, cool gray, etc. Informs background, surface, and card.
• Text: the body text color (most brands use near-black, not pure #000). Informs fg-primary.
• Status colors: any brand-specific green/red for success/error. Inform kpi-positive / kpi-negative.

Step 2: Build the light theme

• Set primary to a saturated, mid-tone color. It powers buttons, selected states, and emphasis, so avoid very light or very dark primaries. If the raw brand color is too light or dark to act as an action color, keep its hue but nudge lightness toward a usable mid-tone.
• Only override background, surface, and card when the brand calls for a distinctly tinted or off-white canvas; otherwise the defaults work well. Keep light backgrounds genuinely light (high lightness, low saturation) — charts and tables assume a light canvas.
• Ensure fg-primary meets WCAG AA contrast (≥ 4.5:1) against the background. Near-black brand text almost always passes; verify if the brand text is a mid-gray.

Step 3: Adapt the dark theme (do not just copy light)

Colors that look correct on white are often too dark, too saturated, or too low-contrast on a dark canvas. Adapt each role:

• Lighten and slightly desaturate primary and secondary so they sit comfortably on a dark surface, while keeping the same hue identity (the dark primary should read as "the same brand color, brighter," not a different hue).
• Avoid pure black and pure white. Use a deep near-neutral background and a soft near-white fg-primary. Pure #000/#fff cause harsh contrast and halation.
• Brighten status colors so kpi-positive / kpi-negative pop against the dark canvas.
• Re-check contrast against the dark background, not the light one.

Data visualization palette guidelines

Setting primary does not populate the chart palettes. To make charts on-brand, set color-qualitative-*, color-sequential-*, and color-diverging-* explicitly in both light: and dark:. For these palettes, legibility and analytical correctness come first, brand fidelity second.

Qualitative palette (categorical data)

Used for dimension values, series, and legend entries. Up to 24 colors; the earliest entries are used most, so they matter most.

• Lead with the brand: make color-qualitative-1 (and ideally -2) the brand primary and secondary, so common single- and two-series charts read on-brand.
• Maximize distinguishability after the first one or two: walk around the hue wheel (e.g. indigo → pink → cyan → amber → green → purple → red → teal) rather than clustering near the brand hue. Adjacent entries should differ clearly in hue and/or lightness.
• Hold lightness and saturation roughly constant so no single category pops just because it is brighter.
• Be colorblind-aware: do not rely on red/green adjacency to carry meaning; vary lightness alongside hue.
• In dark mode, shift the whole palette lighter so every color stays visible against the dark canvas.
• You need not define all 24 — define as many as the brand supports with clear separation; Rill cycles through what you provide.

Sequential palette (ordered / quantitative data)

Used for heatmaps, choropleths, and intensity scales. Nine steps.

• Use a single hue (ideally the brand hue) with monotonic, perceptually even lightness from light to dark.
• Orientation differs by mode: in light mode, -1 is the lightest and -9 the darkest; in dark mode, reverse it so -1 is the darkest and -9 the lightest. In both modes -1 sits closest to the background and -9 is the most prominent.

Diverging palette (data with a meaningful midpoint)

Used for deviation from a baseline, change vs. prior period, or above/below target. Eleven steps.

• Two contrasting hues meeting at a neutral midpoint (-6): light gray in light mode, dark gray/slate in dark mode.
• Map semantics intentionally (conventionally negative on one end, positive on the other) and keep the two arms symmetric in intensity so neither side looks more important.
• Prefer hue pairs that survive color-vision deficiency (e.g. blue↔red, or brand-hue↔complement) over red↔green alone; if using red↔green, keep a clear lightness difference between the arms.

Minimal Theme Example

If you only need to set brand colors without customizing palettes, use this minimal structure:

# themes/brand.yaml
type: theme

light:
  primary: "#0369a1"
  secondary: "#06b6d4"

dark:
  primary: "#38bdf8"
  secondary: "#22d3ee"

Legacy Format

Older Rill projects may use a simpler format with a top-level colors: block. This format is still supported but deprecated in favor of the light:/dark: structure:

# Legacy format (deprecated)
type: theme
colors:
  primary: "#FF6A00"
  secondary: "#0F46A3"

Reference documentation

Here is a full JSON schema for the theme syntax:

allOf:
    - properties:
        colors:
            additionalProperties: true
            description: Color palette for the theme
            properties:
                primary:
                    description: Primary color
                    type: string
                secondary:
                    description: Secondary color
                    type: string
            type: object
        dark:
            description: Dark theme color configuration
            properties:
                kpi-negative:
                    description: Color for negative KPI delta values in dark theme. Defaults to red.
                    type: string
                kpi-positive:
                    description: Color for positive KPI delta values in dark theme. Defaults to fg-secondary (gray).
                    type: string
                primary:
                    description: Primary color for dark theme. Can have any hex, [named colors](https://www.w3.org/TR/css-color-4/#named-colors) or hsl() formats.
                    type: string
                secondary:
                    description: Secondary color for dark theme. Can have any hex, [named colors](https://www.w3.org/TR/css-color-4/#named-colors) or hsl() formats.
                    type: string
                variables:
                    additionalProperties:
                        type: string
                    description: Custom CSS variables for dark theme
                    type: object
            type: object
        light:
            description: Light theme color configuration
            properties:
                kpi-negative:
                    description: Color for negative KPI delta values in light theme. Defaults to red.
                    type: string
                kpi-positive:
                    description: Color for positive KPI delta values in light theme. Defaults to fg-secondary (gray).
                    type: string
                primary:
                    description: Primary color for light theme. Can have any hex, [named colors](https://www.w3.org/TR/css-color-4/#named-colors) or hsl() formats.
                    type: string
                secondary:
                    description: Secondary color for light theme. Can have any hex, [named colors](https://www.w3.org/TR/css-color-4/#named-colors) or hsl() formats.
                    type: string
                variables:
                    additionalProperties:
                        type: string
                    description: Custom CSS variables for light theme
                    type: object
            type: object
        type:
            const: theme
            description: Refers to the resource type and must be `theme`
            type: string
      required:
        - type
      title: Properties
      type: object
    - $ref: '#/definitions/common_properties'
description: |
    In your Rill project directory, create a `<theme_name>.yaml` file in any directory containing `type: theme`. Rill will automatically ingest the theme next time you run `rill start` or deploy to Rill Cloud.

    To apply that theme to a dashboard, add `default_theme: <name of theme>` to the yaml file for that dashboard. Alternatively, you can add this to the end of the URL in your browser: `?theme=<name of theme>`
examples:
    - dark:
        primary: '#818CF8'
        secondary: '#A78BFA'
      light:
        primary: '#4F46E5'
        secondary: '#8B5CF6'
      type: theme
    - dark:
        color-sequential-1: hsl(180deg 40% 30%)
        color-sequential-5: hsl(180deg 50% 50%)
        color-sequential-9: hsl(180deg 60% 70%)
        primary: 2DD4BF
        secondary: 34D399
      light:
        color-qualitative-1: hsl(156deg 56% 52%)
        color-qualitative-2: hsl(27deg 100% 65%)
        color-sequential-1: hsl(180deg 80% 95%)
        color-sequential-5: hsl(180deg 80% 50%)
        color-sequential-9: hsl(180deg 80% 25%)
        primary: '#14B8A6'
        secondary: '#10B981'
      type: theme
    - dark:
        kpi-negative: '#f87171'
        kpi-positive: '#4ade80'
        primary: '#818cf8'
        secondary: '#a78bfa'
      light:
        kpi-negative: '#dc2626'
        kpi-positive: '#16a34a'
        primary: '#6366f1'
        secondary: '#8b5cf6'
      type: theme
id: themes
title: Theme YAML
type: object