public ColorReference brighten(final Float brightness) {
		ColorReference copy = copy();
		if (copy.brightness == null) {
			copy.brightness = brightness;
		} else {
			copy.brightness += brightness;
		}
		return copy;
	}
public ColorReference brighten ( final Float brightness ) { ColorReference copy = copy ( ) ; if ( copy . brightness == null ) { copy . brightness = brightness ; } else { copy . brightness += brightness ; } return copy ; }
Brightens this color by the amount given. Returns a copy of this color
object not this object itself.

@param brightness
the amount to brighten (between 0 and 1).
@return a copy of this color object, brightened by the given amount.