algorithmic-color-palette（算法调色板）

Algorithmic Colour Palette

A brand palette of 2–3 colours is not enough for a UI. You need shades for states (hover, active, disabled), neutrals for backgrounds and borders, and semantic colours for status. Deriving these algorithmically from the brand colours produces a palette that feels coherent — everything is visually related to the brand rather than pulled from a generic grey or a stock colour library.

Deriving Interactive State Colours

From each brand colour, generate at minimum three variants: base, darker (hover/active), lighter (tint/background).

Method: HSL adjustment

base:    hsl(H, S%, L%)
hover:   hsl(H, S%, L% - 8%)     ← darken by reducing lightness
active:  hsl(H, S%, L% - 14%)    ← darken further
tint:    hsl(H, S%, L% + 40%)    ← lighten significantly for backgrounds
subtle:  hsl(H, S% * 0.3, L% + 45%)  ← heavily desaturated, near-white

Example: brand primary #133174 (hsl 224, 70%, 27%)

--color-primary-subtle:  hsl(224, 21%, 94%);  /* background tint */
--color-primary-tint:    hsl(224, 70%, 67%);  /* light variant */
--color-primary:         hsl(224, 70%, 27%);  /* base */
--color-primary-hover:   hsl(224, 70%, 19%);  /* hover: -8% lightness */
--color-primary-active:  hsl(224, 70%, 13%);  /* active: -14% lightness */

Example: success green derived from a teal brand colour

If the brand has a green or teal, shift it toward a clearer success green:

--color-success-subtle:  hsl(142, 20%, 94%);
--color-success:         hsl(142, 60%, 35%);
--color-success-hover:   hsl(142, 60%, 27%);

Deriving Brand-Tinted Greys

Generic greys (#666, #999, #eee) feel disconnected from the brand. Desaturating the brand hue produces greys that are subtly tinted — warm, cool, or neutral depending on the brand — and feel like they belong to the same palette.

Optical Comfort: Avoiding Pure Black on White

Extreme contrast (pure black #000000 on pure white #FFFFFF) can cause "halation" and eye strain. To create a more comfortable reading experience:

• Use "Near-Black" for text: Use a very dark grey (e.g., #222222 or your grey-900 token) instead of pure black.
• Use "Off-White" for backgrounds: A slightly muted white (e.g., #EEEEEE or your grey-50 token) is softer on the eyes than pure #FFFFFF.

This "softened contrast" remains highly accessible (passing WCAG AA/AAA) but feels more professional and less harsh.

Method: desaturate + adjust lightness

brand hue H
grey-900: hsl(H, 12%, 10%)   ← near-black, text
grey-700: hsl(H, 10%, 30%)   ← dark text, icons
grey-500: hsl(H,  8%, 50%)   ← secondary text, placeholders
grey-300: hsl(H,  6%, 70%)   ← disabled text, subtle labels
grey-200: hsl(H,  5%, 82%)   ← borders, dividers
grey-100: hsl(H,  4%, 92%)   ← input backgrounds, table stripes
grey-50:  hsl(H,  3%, 96%)   ← page background, subtle fills

Example: brand primary #133174 (H = 224, blue-tinted)

--color-grey-900: hsl(224, 12%, 10%);  /* #16171f — slightly blue-black */
--color-grey-500: hsl(224,  8%, 50%);  /* #7b7e8a — cool grey */
--color-grey-200: hsl(224,  5%, 82%);  /* #cfd0d5 — cool light border */
--color-grey-50:  hsl(224,  3%, 96%);  /* #f4f4f6 — near-white with a hint of blue */

Compare to generic #f5f5f5 (no hue) — the brand-tinted version is subtly different but feels intentional.

Semantic Colour Derivation

Status colours (error, warning, success, info) should feel harmonious with the brand. To achieve cohesion, align their Saturation and Lightness to create a consistent "visual weight" across the status set.

Method: Aligned visual weight

1. Pick the Hues: Use standard semantic hues (0 for Error, 38 for Warning, 142 for Success).
2. Align S & L: Use the saturation and lightness of your Brand Primary as a starting point.
3. Adjust for Perceived Brightness: Hues like Yellow/Orange (Warning) feel brighter than Blue/Red. Reduce the lightness of Warning by 5–10% compared to Success or Error to ensure they feel equally "heavy" on the page.

The "Vibrancy" Rule: If the brand is muted (low saturation), the semantic colours should also be slightly muted. If the brand is neon/vibrant, the semantics should follow suit. Cohesion comes from shared intensity.

Functional and Interactive Colours

Standard UI elements require dedicated functional tokens beyond basic brand and semantic colours.

Focus States

Focus indicators are critical for accessibility. Use a high-visibility colour that works on all backgrounds.

• Default: Brand Primary (if contrast is high enough).
• Fallback: A dedicated high-contrast blue hsl(215, 95%, 50%).
• Token: --color-focus.

Selection and Highlights

Text selection and list item highlights should be subtle and non-distracting.

• Method: Use the primary hue with very high lightness (90%+) and moderate saturation.
• Token: --color-selection.

Overlays and Modals

Backdrops for modals or drawers need a neutral, semi-transparent colour.

• Method: Use your grey-900 hue with an alpha channel.
• Token: --color-overlay: hsla(H, 12%, 10%, 0.5);

Skeleton and Loading

Loading states should be neutral and recessive.

• Method: Use grey-200 as the base and grey-100 as the shimmer highlight.
• Token: --color-skeleton.

Disabled States

Disabled elements must communicate unreachability.

• Method: Use grey-500 for text and grey-200 for backgrounds/borders.
• Rule: Avoid using brand tints for disabled backgrounds to prevent "pseudo-active" confusion.

Brand-Tinted Shadows

Premium UIs avoid pure black shadows. Use a very dark, desaturated brand hue.

• Method: hsla(H, 15%, 5%, alpha) where H is the brand hue.
• Token: --color-shadow-base.

Links

• Base: Brand Primary or a dedicated high-visibility blue.
• Visited: Shift primary hue toward purple (+20) and reduce saturation.
• Token: --color-link, --color-link-visited.

Input and Validation

• Method: Use semantic base colours for borders and text in error/success states.
• Inactive Border: grey-200.
• Active/Focus Border: Brand Primary.

Full Token Output Example

:root {
  /* Primary — derived from brand #133174 */
  --color-primary-subtle:  hsl(224, 21%, 94%);
  --color-primary-tint:    hsl(224, 70%, 67%);
  --color-primary:         hsl(224, 70%, 27%);
  --color-primary-hover:   hsl(224, 70%, 19%);
  --color-primary-active:  hsl(224, 70%, 13%);

  /* Brand-tinted neutrals */
  --color-grey-900: hsl(224, 12%, 10%);
  --color-grey-700: hsl(224, 10%, 30%);
  --color-grey-500: hsl(224,  8%, 50%);
  --color-grey-300: hsl(224,  6%, 70%);
  --color-grey-200: hsl(224,  5%, 82%);
  --color-grey-100: hsl(224,  4%, 92%);
  --color-grey-50:  hsl(224,  3%, 96%);

  /* Semantic */
  --color-error:   hsl(4,  72%, 44%);
  --color-warning: hsl(38, 80%, 44%);
  --color-success: hsl(142, 58%, 35%);
  --color-info:    hsl(224, 70%, 27%); /* = primary */

  /* Semantic subtle backgrounds */
  --color-error-subtle:   hsl(4,  50%, 95%);
  --color-warning-subtle: hsl(38, 60%, 95%);
  --color-success-subtle: hsl(142, 40%, 95%);

  /* Functional */
  --color-focus:     var(--color-primary);
  --color-selection: hsl(224, 70%, 90%);
  --color-overlay:   hsla(224, 12%, 10%, 0.5);
  --color-skeleton:  var(--color-grey-200);
  --color-shadow:    hsla(224, 15%, 5%, 0.1);

  /* Links */
  --color-link:         var(--color-primary);
  --color-link-visited: hsl(244, 40%, 35%);
}

Review Checklist

• Are hover and active colours derived from the base by lightness adjustment, not chosen independently?
• Are neutral greys tinted with the brand hue rather than using generic #666 / #eee?
• Is saturation reduced progressively as lightness increases in the grey scale?
• Is pure black (#000000) on pure white (#FFFFFF) avoided in favor of near-blacks (e.g., #222) and off-whites (e.g., #EEE)?
• Are status colours (Success, Warning, Error) visually weighted to match the brand primary?
• If the brand primary is orange or amber, is warning colour clearly distinct from it?
• Does each brand colour have at minimum: subtle, base, hover, active variants?
• Are semantic colours aligned in Saturation and Lightness to create a cohesive visual weight?
• Is there a dedicated --color-focus token that meets accessibility contrast requirements?
• Are selection, overlay, and shadow colours derived from the brand hue rather than generic black/grey?
• Are disabled states neutral (greys) to avoid confusion with interactive brand colours?
• Does the link colour have a distinct visited state derived algorithmically?

Common Anti-Patterns