/**
 * Color utilities shared by notification components (`Alert`, `Toast`, …).
 *
 * Used by any component that accepts a `color` prop and needs to auto-derive
 * readable text/icon colors, darkened border/accent shades, or luminance checks.
 *
 * Theme colors are `rgba(r, g, b, a)` strings. Arbitrary CSS colors passed by
 * consumers may be hex (`#rrggbb`) or any valid CSS color. Functions here handle
 * both formats and fall back gracefully (returning the original string) for
 * formats they cannot parse.
 */
/**
 * Returns `true` when the color is perceptually dark enough to need light
 * text/icons on top of it.
 *
 * Uses the WCAG luminance threshold (L < 0.179 ≈ midpoint between black and
 * "mid-grey" at contrast ratio ~3:1 against white).
 */
export declare function isColorDark(color: string): boolean;
/**
 * Returns a darkened version of the color by **reducing HSL lightness** by
 * `amount` (default 0.35 → 35 percentage points darker).
 *
 * Converting through HSL preserves the hue and saturation so light pastel
 * colors (e.g. `greenLighter`) darken to a recognizable mid-shade of the same
 * hue rather than washing out to grey (which a naïve per-channel multiply does).
 *
 * Falls back to the original string when the color format is not parsable
 * (e.g. CSS named colors, `hsl()`, `color-mix()`).
 */
export declare function darkenColor(color: string, amount?: number): string;
/**
 * Returns either `'rgba(255, 255, 255, 1)'` (white) or `'rgba(43, 45, 49, 1)'`
 * (greyDarker) depending on whether the background color is perceived as dark
 * or light.
 *
 * Intended for computing readable text/icon colors on a custom background.
 *
 * @param bgColor - The background color to contrast against.
 * @param darkText - The dark text color to use on light backgrounds.
 *                   Defaults to `rgba(43, 45, 49, 1)` (theme `greyDarker`).
 * @param lightText - The light text color to use on dark backgrounds.
 *                    Defaults to `rgba(255, 255, 255, 1)` (white).
 */
export declare function getContrastColor(bgColor: string, darkText?: string, lightText?: string): string;
