Way overboard on a cool script posted by Rlemon

RainbowBright.js

function r() {
    return Math.floor(Math.random() * 255);
}

function lemon() {
  var cycle = parseFloat(this.dataset.cycle);

	if(isNaN(cycle)){
		cycle = ~~(Math.random()*100);
	}

  with(this.style) {
	  var matchColor = /rgb\((\d{1,3}), (\d{1,3}), (\d{1,3})\)/,
		    match = matchColor.exec(color),
		    mColor = {r:r(), g:r(), b:r()},
		    bColor = {r:r(), g:r(), b:r()};
	
		if(match !== null) {
			mColor = {r:match[1], g:match[2], b:match[3]}
		}
		
		match = matchColor.exec(backgroundColor);
		
		if(match !== null) {
			bColor = {r:match[1], g:match[2], b:match[3]};
		}
		
		cycle+=0.5;
		
		if(cycle>100){
			cycle = 0;   
		}
		
		cCycle = cycle + 50;
		if(cCycle>100){
			cCycle -= 100;   
		}
	
	  colorCycle(mColor, cCycle);
	  colorCycle(bColor, cycle);

    color = "rgb(" +mColor.r+","+mColor.g+","+mColor.b+")";
    backgroundColor = "rgb(" +bColor.r+","+bColor.g+","+bColor.b+")";
  }
	this.dataset.cycle = cycle;
}

function rocks() {
    Array.prototype.forEach.call(document.all, function(item) {
        setTimeout(function() {
            lemon.call(item);
        }, 10);
    });
    setTimeout(rocks, 10);
}

function colorCycle(color, cycle){	
    color.r = ~~(Math.sin(.3*cycle + 0) * 127+ 128);
    color.g = ~~(Math.sin(.3*cycle + 2) * 127+ 128);
    color.b = ~~( Math.sin(.3*cycle + 4) * 127+ 128);
}

rocks();

Why are you still using with(){}... I used it mostly as a jest hehehe.