src/vs/workbench/browser/parts/panel/panelPart.ts/BasePanelPart/updateStyles
class BasePanelPart:	override updateStyles(): void {
		super.updateStyles();

		const container = assertIsDefined(this.getContainer());
		container.style.backgroundColor = this.getColor(this.backgroundColor) || '';
		const borderColor = this.getColor(contrastBorder) || '';
		container.style.borderLeftColor = borderColor;
		container.style.borderRightColor = borderColor;

		const title = this.getTitleArea();
		if (title) {
			title.style.borderTopColor = this.getColor(contrastBorder) || '';
		}
	}