offsetHSL( h, s, l ) {

		this.getHSL( _hslA );

		return this.setHSL( _hslA.h + h, _hslA.s + s, _hslA.l + l );

	}
Adds the given HSL values to this color's values.
Internally, this converts the color's RGB values to HSL, adds HSL
and then converts the color back to RGB.

@param {number} h - Hue value between `0.0` and `1.0`.
@param {number} s - Saturation value between `0.0` and `1.0`.
@param {number} l - Lightness value between `0.0` and `1.0`.
@return {Color} A reference to this color.