kyle-Programming Problem: Manipulating Hex colors

hex_colors.js

function percentToHex(x, y) {
    var c1 = '000000',
        hex = ['0', '1','2','3','4','5','6','7','8','9','A', 'B', 'C', 'D', 'E', 'F'],
        second = hex[Math.round(x*(hex.length-1))],
        first= hex[Math.round(y*(hex.length-1))],
        group = first+""+second,
        hexStr = group+""+group+group;
    return hexStr;
}

function addHexColor(c1, c2) {
  var hexStr = (parseInt(c1, 16) + parseInt(c2, 16)).toString(16);
  while (hexStr.length < 6) { hexStr = '0' + hexStr; } // Zero pad.
  return hexStr;
}