src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/updateStyles
class EditorGroupView:	protected override updateStyles(): void {
		const isEmpty = this.isEmpty;

		// Container
		if (isEmpty) {
			this.element.style.backgroundColor = this.getColor(EDITOR_GROUP_EMPTY_BACKGROUND) || '';
		} else {
			this.element.style.backgroundColor = '';
		}

		// Title control
		const borderColor = this.getColor(EDITOR_GROUP_HEADER_BORDER) || this.getColor(contrastBorder);
		if (!isEmpty && borderColor) {
			this.titleContainer.classList.add('title-border-bottom');
			this.titleContainer.style.setProperty('--title-border-bottom-color', borderColor.toString());
		} else {
			this.titleContainer.classList.remove('title-border-bottom');
			this.titleContainer.style.removeProperty('--title-border-bottom-color');
		}

		const { showTabs } = this.accessor.partOptions;
		this.titleContainer.style.backgroundColor = this.getColor(showTabs ? EDITOR_GROUP_HEADER_TABS_BACKGROUND : EDITOR_GROUP_HEADER_NO_TABS_BACKGROUND) || '';

		// Editor container
		this.editorContainer.style.backgroundColor = this.getColor(editorBackground) || '';
	}