src/vs/workbench/browser/parts/auxiliarybar/auxiliaryBarPart.ts/AuxiliaryBarPart/updateStyles
class AuxiliaryBarPart:	override updateStyles(): void {
		super.updateStyles();

		const container = assertIsDefined(this.getContainer());
		const borderColor = this.getColor(SIDE_BAR_BORDER) || this.getColor(contrastBorder);
		const isPositionLeft = this.layoutService.getSideBarPosition() === Position.RIGHT;

		container.style.color = this.getColor(SIDE_BAR_FOREGROUND) || '';

		container.style.borderLeftColor = borderColor ?? '';
		container.style.borderRightColor = borderColor ?? '';

		container.style.borderLeftStyle = borderColor && !isPositionLeft ? 'solid' : 'none';
		container.style.borderRightStyle = borderColor && isPositionLeft ? 'solid' : 'none';

		container.style.borderLeftWidth = borderColor && !isPositionLeft ? '1px' : '0px';
		container.style.borderRightWidth = borderColor && isPositionLeft ? '1px' : '0px';
	}