src/vs/workbench/browser/parts/compositeBarActions.ts/ActivityActionViewItem/updateStyles
class ActivityActionViewItem:	protected updateStyles(): void {
		const theme = this.themeService.getColorTheme();
		const colors = this.options.colors(theme);

		if (this.label) {
			if (this.options.icon) {
				const foreground = this._action.checked ? colors.activeBackgroundColor || colors.activeForegroundColor : colors.inactiveBackgroundColor || colors.inactiveForegroundColor;
				if (this.activity.iconUrl) {
					// Apply background color to activity bar item provided with iconUrls
					this.label.style.backgroundColor = foreground ? foreground.toString() : '';
					this.label.style.color = '';
				} else {
					// Apply foreground color to activity bar items provided with codicons
					this.label.style.color = foreground ? foreground.toString() : '';
					this.label.style.backgroundColor = '';
				}
			} else {
				const foreground = this._action.checked ? colors.activeForegroundColor : colors.inactiveForegroundColor;
				const borderBottomColor = this._action.checked ? colors.activeBorderBottomColor : null;
				this.label.style.color = foreground ? foreground.toString() : '';
				this.label.style.borderBottomColor = borderBottomColor ? borderBottomColor.toString() : '';
			}

			this.container.style.setProperty('--insert-border-color', colors.dragAndDropBorder ? colors.dragAndDropBorder.toString() : '');
		}

		// Badge
		if (this.badgeContent) {
			const badgeForeground = colors.badgeForeground;
			const badgeBackground = colors.badgeBackground;
			const contrastBorderColor = theme.getColor(contrastBorder);

			this.badgeContent.style.color = badgeForeground ? badgeForeground.toString() : '';
			this.badgeContent.style.backgroundColor = badgeBackground ? badgeBackground.toString() : '';

			this.badgeContent.style.borderStyle = contrastBorderColor ? 'solid' : '';
			this.badgeContent.style.borderWidth = contrastBorderColor ? '1px' : '';
			this.badgeContent.style.borderColor = contrastBorderColor ? contrastBorderColor.toString() : '';
		}
	}