src/vs/editor/contrib/colorPicker/colorPickerWidget.ts/ColorPickerBody/onDidOpacityChange
class ColorPickerBody:	private onDidOpacityChange(a: number): void {
		const hsva = this.model.color.hsva;
		this.model.color = new Color(new HSVA(hsva.h, hsva.s, hsva.v, a));
	}