import type { NamedCSSColour } from "./types";
/**
 * Determines whether a string represents a valid CSS RGB or RGBA colour value.
 *
 * Captures the following CSS RGB formats:
 * - `rgb(0,0,0)`
 * - `rgba(0, 0, 0, 0.4)`
 * - `rgba(0,0,0,50%)`
 * - `rgb(0 0 0)`
 * - `rgba(0 0 0 / 0.4)`
 * - `rgb(0 0 0 / 0.5)`
 * - `rgb(0 0 0 / 50%)`
 * - `rgb(50%, 25%, 100%)`
 * - `rgba(50%, 25%, 100%, 0.8)`
 * - `rgba(50%, 25%, 100%, 80%)`
 *
 * @param {string} colour - The string to test.
 * @returns {boolean} `true` if the string represents a valid CSS RGB or RGBA colour value, `false` otherwise.
 */
export declare function isCSSRGBColour(colour: string): boolean;
/**
 * Determines whether a string represents a valid hexadecimal colour value.
 *
 * @param {string} colour - The string to test.
 * @returns {boolean} True if the string represents a valid hexadecimal colour value, false otherwise.
 */
export declare function isHexColour(colour: string): boolean;
/**
 * Determines whether a string represents a valid named CSS colour.
 *
 * @param {NamedCSSColour} colour - The string to test.
 * @returns {boolean} `true` if the string represents a valid named CSS colour, `false` otherwise.
 */
export declare function isNamedCSSColour(colour: NamedCSSColour): colour is NamedCSSColour;