src/vs/workbench/common/theme.ts/WORKBENCH_BACKGROUND
export function WORKBENCH_BACKGROUND(theme: IColorTheme): Color {
	switch (theme.type) {
		case 'dark':
			return Color.fromHex('#252526');
		case 'light':
			return Color.fromHex('#F3F3F3');
		default:
			return Color.fromHex('#000000');
	}
}