/**
 * Function that takes a valid CSS color and adds some opacity to it.
 *
 * @param baseColor Color in HSL, HSV, HEX or RGB
 * @param alpha Alpha for this color
 */
export declare function toRGBA(baseColor: string, alpha: number): string;
/**
 * Function that takes a valid CSS color and mixes it with black.
 *
 * @param baseColor Color in HSL, HSV, HEX or RGB
 * @param amount Amount of black to mix with the base color.
 */
export declare function darken(baseColor: string, amount?: number): string;