How to get a random color in my create.js shape?

I want to have a random color where "Crimson" is defined

    var stage = new createjs.Stage("demoCanvas");

    var circle = new createjs.Shape();
    circle.graphics.beginFill("Crimson").drawCircle(0, 0, 50);
    circle.x = 100;
    circle.y = 100;
    stage.addChild(circle);
    stage.update();