原文地址：http://www.cnblogs.com/vaal-water/archive/2013/04/08/3008880.html

自己试过很好用

function zero_fill_hex(num, digits) {  var s = num.toString(16);  while (s.length < digits)    s = "0" + s;  return s;}function rgb2hex(rgb) {  if (rgb.charAt(0) == '#')    return rgb;   var ds = rgb.split(/\D+/);  var decimal = Number(ds[1]) * 65536 + Number(ds[2]) * 256 + Number(ds[3]);  return "#" + zero_fill_hex(decimal, 6);}