public String toString() {
        if (this.equals(Color.White))
            return Constant.Color.White;
        else if (this.equals(Color.Green))
            return Constant.Color.Green;
        else if (this.equals(Color.Red))
            return Constant.Color.Red;
        else if (this.equals(Color.Black))
            return Constant.Color.Black;
        else if (this.equals(Color.Blue))
            return Constant.Color.Blue;
        else
            return Constant.Color.Colorless;
    }