src/vs/platform/theme/electron-main/themeMainService.ts/ThemeMainService/getBackgroundColor
class ThemeMainService:	getBackgroundColor(): string {
		const colorScheme = this.getColorScheme();
		if (colorScheme.highContrast && this.configurationService.getValue('window.autoDetectHighContrast')) {
			return colorScheme.dark ? DEFAULT_BG_HC_BLACK : DEFAULT_BG_HC_LIGHT;
		}

		let background = this.stateMainService.getItem<string | null>(THEME_BG_STORAGE_KEY, null);
		if (!background) {
			const baseTheme = this.stateMainService.getItem<string>(THEME_STORAGE_KEY, 'vs-dark').split(' ')[0];
			switch (baseTheme) {
				case 'vs': background = DEFAULT_BG_LIGHT; break;
				case 'hc-black': background = DEFAULT_BG_HC_BLACK; break;
				case 'hc-light': background = DEFAULT_BG_HC_LIGHT; break;
				default: background = DEFAULT_BG_DARK;
			}
		}

		if (isMacintosh && background.toUpperCase() === DEFAULT_BG_DARK) {
			background = '#171717'; // https://github.com/electron/electron/issues/5150
		}

		return background;
	}