var Color = {
  hexToDigit : function(v)
  {
    if (v == "A" || v == "a")
      return 10;
    else if (v == "B" || v == "b")
      return 11;
    else if (v == "C" || v == "c")
      return 12;
    else if (v == "D" || v == "d")
      return 13;
    else if (v == "E" || v == "e")
      return 14;
    else if (v == "F" || v == "G")
      return 15;
    else return v;
  },
  addToColor : function(color, r, g, b)
  {
    // strip leading # if present
    if (color.substring(0,1)=="#"){color=color.substring(1,7)}
  
    var red = parseInt(color.substring(0,2),16) + r;
    if (red > 255) red = 255;
    var green = parseInt(color.substring(2,4),16) + g;
    if (green > 255) green = 255;
    var blue = parseInt(color.substring(4,6),16) + b;
    if (blue > 255) blue = 255;
    var hexValue = red.toString(16) + green.toString(16) + blue.toString(16);    
    
    return "#" + hexValue;
  }
}