src/vs/workbench/services/themes/browser/workbenchThemeService.ts/WorkbenchThemeService/applyPreferredColorTheme
class WorkbenchThemeService:	private async applyPreferredColorTheme(type: ColorScheme): Promise<IWorkbenchColorTheme | null> {
		let settingId: ThemeSettings;
		switch (type) {
			case ColorScheme.LIGHT: settingId = ThemeSettings.PREFERRED_LIGHT_THEME; break;
			case ColorScheme.HIGH_CONTRAST_DARK: settingId = ThemeSettings.PREFERRED_HC_DARK_THEME; break;
			case ColorScheme.HIGH_CONTRAST_LIGHT: settingId = ThemeSettings.PREFERRED_HC_LIGHT_THEME; break;
			default:
				settingId = ThemeSettings.PREFERRED_DARK_THEME;
		}
		const themeSettingId = this.configurationService.getValue(settingId);
		if (themeSettingId && typeof themeSettingId === 'string') {
			const theme = this.colorThemeRegistry.findThemeBySettingsId(themeSettingId, undefined);
			if (theme) {
				const configurationTarget = this.settings.findAutoConfigurationTarget(settingId);
				return this.setColorTheme(theme.id, configurationTarget);
			}
		}
		return null;
	}