RBGtoRGBA

gistfile1

function RGBtoRGBA(red, green, blue) {
    if ((green === void 0) && (typeof red === 'string')) {
        red = red.replace(/^\s*#|\s*$/g, '');
        if (red.length == 3) {
            red = red.replace(/(.)/g, '$1$1');
        }
        green = parseInt(red.substr(2, 2), 16);
        blue = parseInt(red.substr(4, 2), 16);
        red = parseInt(red.substr(0, 2), 16);
    }

    var min, alpha = (255 - (min = Math.min(red, green, blue))) / 255;

    return {
        red: red = 0|( red - min ) / alpha,
        green: green = 0|( green - min ) / alpha,
        blue: blue = 0|( blue - min ) / alpha,
        alpha: alpha = (0|1000*alpha)/1000,
        rgba: 'rgba(' + red + ', ' + green + ', ' + blue + ', ' + alpha + ')'
    };
}

RGBtoRGBA(204, 153, 102)