get random color in hex or rgba format.

randomColor.js

/**
     * @param useRGB Boolean, true for rgba format, false will return color in hex format
     * @param randomAlpha Boolean, when using rgba format, decide whether to randomnize alpha value too
     */
    function getRandomColor( useRGB, randomAlpha ){
        if( useRGB ){
            return "rgba("+
                  Math.floor(Math.random()*256)+","+
                  Math.floor(Math.random()*256)+","+
                  Math.floor(Math.random()*256)+","+
                  (randomAlpha ? Math.random().toFixed(1) : 1) +")";
        }
        return Math.floor(Math.random() * 0xFFFFFF).toString(16);
    }