How to use the fabric.fabric.Color function in fabric

setBrush(setting) {
        const brush = this.getCanvas().freeDrawingBrush;

        setting = setting || {};
        this.width = setting.width || this.width;
        if (setting.color) {
            this.oColor = new fabric.Color(setting.color);
        }
        brush.width = this.width;
        brush.color = this.oColor.toRgba();
    }

constructor(graphics) {
        super(consts.componentNames.FREE_DRAWING, graphics);

        /**
         * Brush width
         * @type {number}
         */
        this.width = 12;

        /**
         * fabric.Color instance for brush color
         * @type {fabric.Color}
         */
        this.oColor = new fabric.Color('rgba(0, 0, 0, 0.5)');
    }

setBrush(setting) {
        const brush = this.getCanvas().freeDrawingBrush;

        setting = setting || {};
        this._width = setting.width || this._width;

        if (setting.color) {
            this._oColor = new fabric.Color(setting.color);
        }
        brush.width = this._width;
        brush.color = this._oColor.toRgba();
    }

constructor(graphics) {
        super(consts.componentNames.LINE, graphics);

        /**
         * Brush width
         * @type {number}
         * @private
         */
        this._width = 12;

        /**
         * fabric.Color instance for brush color
         * @type {fabric.Color}
         * @private
         */
        this._oColor = new fabric.Color('rgba(0, 0, 0, 0.5)');

        /**
         * Listeners
         * @type {object.}
         * @private
         */
        this._listeners = {
            mousedown: this._onFabricMouseDown.bind(this),
            mousemove: this._onFabricMouseMove.bind(this),
            mouseup: this._onFabricMouseUp.bind(this)
        };
    }