Now the we can talk to the lights, It’s time to deal with colours. We can’t just send RGB to the API, so I made a class that displays a rectangle of colours, and can convert from HSL to RGB for displaying each one. The HslToRgb function I stole from stackoverflow.

package;

import openfl.display.Sprite;
import openfl.events.MouseEvent;
import openfl.events.Event;


class Colours extends Sprite {
	private var _width:Int = 60; // Number of hues
	private var _height:Int = 30; // Number of saturations
	private var size:Int = 10;
	
	public var h:Float;
	public var s:Float;
	
	
	public function new() {
		super();
		var l = .9;
		for(x in 0..._width) {
			for(y in 0..._height) {
				var h = _height/2;
				var lo = (1-(y/_height/2)); // This is so it fades into white rather than grey
			
				var rgb = hslToRgb( x*1.00/_width, y*1.00/_height, lo);
				var c = rgb[0];
				c = (c<<8) + rgb[1];
				c = (c<<8) + rgb[2];
				graphics.beginFill(c);
				graphics.drawRect(x*size,y*size,size, size);
				graphics.endFill();
			}
		}
		addEventListener(MouseEvent.CLICK, onclick);
		addEventListener(MouseEvent.MOUSE_MOVE, onmove); // So it picks up finger drags
	}
	
	private function onmove(e:MouseEvent) {	
		if ( !e.buttonDown ) return;
		onclick(e);
	}
	private function onclick(e:MouseEvent) {
		h = Math.min(1, e.localX/size/_width);
		s = Math.min(1, e.localY/size/_height);
		var l = 0.5; // This is alpha
		var rgb = hslToRgb(h,s,l); 
		dispatchEvent( new Event(Event.CHANGE) );
	}
	
	/**
	* Converts an HSL color value to RGB. Conversion formula
	* adapted from http://en.wikipedia.org/wiki/HSL_color_space.
	* Assumes h, s, and l are contained in the set [0, 1] and
	* returns r, g, and b in the set [0, 255].
	*
	* @param   Number  h       The hue
	* @param   Number  s       The saturation
	* @param   Number  l       The lightness
	* @return  Array           The RGB representation
	*/
	public function hslToRgb(h:Float, s:Float, l:Float):Array{
		var r:Float, g:Float, b:Float;
	
		if(s == 0){
			r = g = b = l; // achromatic
		}else{
			var hue2rgb = function hue2rgb(p:Float, q:Float, t:Float):Float{
				if(t < 0) t += 1;
				if(t > 1) t -= 1;
				if(t < 1/6) return (p + (q - p) * 6 * t);
				if(t < 1/2) return (q);
				if(t < 2/3) return (p + (q - p) * (2/3 - t) * 6);
				return (p);
			}
	
			var q:Float = l < 0.5 ? l * (1 + s) : l + s - l * s;
			var p:Float = 2 * l - q;
			r = hue2rgb(p, q, h + 1/3);
			g = hue2rgb(p, q, h);
			b = hue2rgb(p, q, h - 1/3);
		}
	
		return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
	}
}