if (this.checked) {
            this.renderer.setElementStyle(this.el.nativeElement.children[0], 'background-color', '#3f51b5');
            this.renderer.setElementStyle(this.el.nativeElement.children[0], 'border-color', '#3f51b5');
        } else {
            this.renderer.setElementStyle(this.el.nativeElement.children[0], 'background-color', '#fff');