Method to lighten / darken hex colors using Javascript.

color.lighten.js

var LightenColor = function(color, percent) {
  	var num = parseInt(color,16),
		amt = Math.round(2.55 * percent),
		R = (num >> 16) + amt,
		B = (num >> 8 & 0x00FF) + amt,
		G = (num & 0x0000FF) + amt;

		return (0x1000000 + (R<255?R<1?0:R:255)*0x10000 + (B<255?B<1?0:B:255)*0x100 + (G<255?G<1?0:G:255)).toString(16).slice(1);
};