src/vs/platform/theme/electron-main/themeMainService.ts/ThemeMainService/saveWindowSplash
class ThemeMainService:	saveWindowSplash(windowId: number | undefined, splash: IPartsSplash): void {

		// Update in storage
		this.stateMainService.setItems([
			{ key: THEME_STORAGE_KEY, data: splash.baseTheme },
			{ key: THEME_BG_STORAGE_KEY, data: splash.colorInfo.background },
			{ key: THEME_WINDOW_SPLASH, data: splash }
		]);

		// Update in opened windows
		if (typeof windowId === 'number') {
			this.updateBackgroundColor(windowId, splash);
		}
	}