Igniteui React Customize Theme

Ignite UI for React — Theming

How the palette actually works

Every palette role (primary, secondary, surface, gray, info, success, warn, error) exposes shades 50–900 plus a -contrast variant per shade. Shades other than 500 are derived from 500 via relative color functions — the theme CSS defines them as hsl(from var(--ig-primary-500) h calc(s * …) calc(l * …)).

So to rebrand, override the 500 shade and everything else follows:

/* src/index.css — imported AFTER the theme CSS */
:root {
  --ig-primary-500: #0d6efd;
  --ig-secondary-500: #ff9800;
}

There are no --ig-primary-h / -s / -l tokens. Writing them is a silent no-op — a common and hard-to-spot mistake. The same applies to --ig-surface-h, --ig-gray-h, and every other -h/-s/-l name.

Always reference palette tokens rather than literals in your own CSS: var(--ig-primary-500), var(--ig-primary-500-contrast) for text on top of it. 50 is lightest, 900 darkest.

Order matters

// main.tsx
import 'igniteui-webcomponents/themes/light/bootstrap.css'; // theme
import 'igniteui-react-grids/grids/themes/light/bootstrap.css'; // grid theme, if using grids
import './index.css'; // your overrides — last

Design systems: bootstrap (default), material, fluent, indigo; each in light and dark.

Global layout knobs

:root {
  --ig-size: 2;          /* 1 small, 2 medium, 3 large */
  --ig-spacing: 1;       /* 0.5 compact … 2 spacious; also -inline / -block variants */
  --ig-radius-factor: 1; /* 0 square … 1 fully rounded */
}

All three cascade, so they scope to a subtree or a single element: igc-button { --ig-size: 1; }.

Component-level overrides

Selectors target the rendered element, never the React name:

igc-avatar {
  --ig-avatar-background: var(--ig-primary-500);
  --ig-avatar-color: var(--ig-primary-500-contrast);
}

igc-input::part(input) { font-size: 1.1rem; }   /* ::part() reaches shadow DOM internals */

Component token names are per-component and not guessable. igc-avatar has --ig-avatar-background, but igc-button exposes only typographic tokens (--ig-button-font-size, …) and has no --ig-button-foreground. Before writing any component token, get the real list: get_component_design_tokens({ component: 'button' }), or read the @cssproperty annotations in node_modules/igniteui-webcomponents/components/<name>/*.d.ts. If a component exposes no token for what you need, use ::part().

Scoping

Palette tokens cascade, so a scoped theme is just custom properties on a container:

.admin { --ig-primary-500: #7c4dff; }

Dark mode

The theme CSS also declares --ig-theme and --ig-theme-variant on :root. Components read those once, globally, from document.documentElement to pick their shadow-DOM styles. Two consequences:

• The variant cannot be scoped to a subtree. Overriding --ig-theme-variant on a wrapper does nothing. Dark mode is an app-wide switch.
• Swapping the stylesheet is not enough at runtime — the value is cached. Call configureTheme, which is re-exported from igniteui-react, to update it and notify mounted components:

import { configureTheme } from 'igniteui-react';

configureTheme('bootstrap', 'dark'); // design system, variant

Prefer a real dark theme file (themes/dark/bootstrap.css) over hand-overriding palette tokens: it re-tunes surface, gray, elevations, and every component schema. See CSS-THEMING.md for the switching patterns.

When choosing colors for a dark palette, surface must be dark (luminance ≤ 0.5) and the gray base must be light. Gray shades are generated to contrast against the surface, so the gray base is always inverted relative to the variant — reversing it produces unreadable text.

Using the igniteui-theming MCP server

Optional but preferred when available — it generates palettes with luminance-safe shades and correct contrast. Verify with detect_platform; if missing, add the config below and tell the user to reload the editor. Pass platform: 'react'.

All tools take named arguments. There is no get_theming_guidance tool — guidance is read through read_resource.

Sequence: create_palette → create_typography / create_elevations → create_theme → per component get_component_design_tokens → create_component_theme with only the tokens that differ from the global theme. Read any luminance warning the tools return instead of ignoring it; if one generated surface color cannot express every depth in the design, use create_custom_palette or define your own --surface-1 / --surface-2 semantic variables.

Never overwrite an existing stylesheet. Propose generated theme code as an edit the user reviews.

VS Code — .vscode/mcp.json (Cursor and Claude Desktop use the same entry under mcpServers):

{
  "servers": {
    "igniteui-theming": {
      "command": "npx",
      "args": ["-y", "igniteui-theming", "igniteui-theming-mcp"]
    }
  }
}

Reference

• CSS-THEMING.md — scoping patterns, CSS Modules, light/dark switching, inline overrides

Related skills

• igniteui-react-components — components, theme CSS setup, slots and events