Colors are Object too !

Color.js

function Color (red,green,blue,alpha) {
    this.red = red;
    this.blue = blue;
    this.green = green;
    this.alpha = (alpha || 1);
}

Color.prototype.toString = function() {
    return "rgba("+Math.floor(this.red) +
        "," + Math.floor(this.green) +
        "," + Math.floor(this.blue) +
        "," +this.alpha + ")";
};

Color.prototype.addRed = function(value) {
    this.red += value;
    if (this.red<0) {
        this.red = 0;
    } else if (this.red >255){
        this.red = 255;
    }
    return this;
};

Color.prototype.addGreen = function(value) {
    this.green += value;
    if (this.green<0) {
        this.green = 0;
    } else if (this.green >255){
        this.green = 255;
    }
    return this;
};

Color.prototype.addBlue = function(value) {
    this.blue += value;
    if (this.blue<0) {
        this.blue = 0;
    } else if (this.blue >255){
        this.blue = 255;
    }
    return this;
};

Color.prototype.lighter = function(value) {
    this.addRed(value);
    this.addGreen(value);
    this.addBlue(value);
    return this;
};

Color.prototype.darker = function(value) {
    this.addRed(-value);
    this.addGreen(-value);
    this.addBlue(-value);
    return this;
};

Color.prototype.set = function(red, green, blue, alpha) {
    this.red = red;
    this.blue = blue;
    this.green = green;
    this.alpha = (alpha || this.alpha);
    return this;
};

Color.prototype.randomize = function(strenght) {
    this.addRed(Math.random()*strenght-strenght/2);
    this.addGreen(Math.random()*strenght-strenght/2);
    this.addBlue(Math.random()*strenght-strenght/2);
    return this;
};

Color.prototype.fadeTo = function(color, percent) {
    this.addRed((color.red-this.red)*percent);
    this.addGreen((color.green-this.green)*percent);
    this.addBlue((color.blue-this.blue)*percent);
};

Color.random = function() {
    var color = new Color(0,0,0);
    color.red = Math.floor(Math.random()*255);
    color.blue = Math.floor(Math.random()*255);
    color.green = Math.floor(Math.random()*255);
    color.alpha = Math.random();
    return color;
};