code: function(color, prc) {
  		var num = parseInt(color, 16),
  		    amt = Math.round(2.55 * prc),
  		    R = (num >> 16) + amt,
  		    G = (num >> 8 & 0x00FF) + amt,
  		    B = (num & 0x0000FF) + amt;
  		return (0x1000000 + (R < 255 ? R < 1 ? 0 : R : 255) * 0x10000 +
  			(G < 255 ? G < 1 ? 0 : G : 255) * 0x100 +
  			(B < 255 ? B < 1 ? 0 : B : 255))
  			.toString(16)
  			.slice(1);
  	}
docs: Change the darkness or lightness