/**
 * Browser-backed color mixing via CSS `color-mix()`.
 *
 * Uses a hidden DOM element + `getComputedStyle` to resolve expressions,
 * cached so each unique expression is computed at most once.
 */
/**
 * Mix two CSS colors using the browser's `color-mix(in srgb)` function.
 *
 * @param color1 - First color (any valid CSS color string)
 * @param color2 - Second color (any valid CSS color string)
 * @param percentage - Percentage of `color1` in the mix (0–100)
 * @returns {string} Resolved color as an `rgb()` string, or `color1` if resolution fails
 */
export declare const mixColor: (color1: string, color2: string, percentage: number) => string;
/**
 * Darken a CSS color by mixing it with black.
 *
 * @param color - Any valid CSS color string
 * @param amount - Darkening intensity from 0 (no change) to 100 (pure black)
 */
export declare const darkenColor: (color: string, amount: number) => string;
/**
 * Lighten a CSS color by mixing it with white.
 *
 * @param color - Any valid CSS color string
 * @param amount - Lightening intensity from 0 (no change) to 100 (pure white)
 */
export declare const lightenColor: (color: string, amount: number) => string;
/**
 * Resolve a CSS color and apply an opacity multiplier to its alpha channel.
 *
 * Unlike setting `element.style.opacity`, this only affects the individual
 * color value — useful when fill and stroke need independent opacity.
 *
 * @param color - Any valid CSS color string
 * @param opacity - Opacity multiplier from 0 to 1 (multiplied with existing alpha)
 * @returns {string} `rgba()` string with the combined alpha, or the original color if resolution fails
 */
export declare const colorWithOpacity: (color: string, opacity: number) => string;
/**
 * Clear the resolved-color cache and detach the probe element.
 * Exposed for test teardown only — not part of the public API.
 */
export declare const resetColorUtilsForTesting: () => void;