function getContrastColor(sColor){
        var oRGB = new RGBColor(sColor);
        var y709 = (oRGB.r * 0.21) + (oRGB.g * 0.72) + (oRGB.b * 0.07);
        return (y709 > 192) ? 'dimgray' : 'white';
    }
Compute a color contrasted with the given color (lightness).
See http://en.wikipedia.org/wiki/Luma_(video)
@param {String} sColor
@returns {String}
@example dimgray if yellow is given.