Bug 296253 [CommonNavigator] An empty label is not properly shown when it is the only contributed label
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentServiceLabelProvider.java
public Color getForeground(Object anElement) {
		ILabelProvider[] labelProviders = contentService.findRelevantLabelProviders(anElement);
		for (int i = 0; i < labelProviders.length; i++) {
			ILabelProvider provider = labelProviders[i];
			if (provider instanceof IColorProvider) {
				IColorProvider colorProvider = (IColorProvider) provider;
				Color color = colorProvider.getForeground(anElement);
				if (color != null) {
					return color;
				}
			}
		}
		return null;
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.IColorProvider#getBackground(java.lang.Object)
	 */
	public Color getBackground(Object anElement) {
		ILabelProvider[] labelProviders = contentService.findRelevantLabelProviders(anElement);
		for (int i = 0; i < labelProviders.length; i++) {
			ILabelProvider provider = labelProviders[i];
			if (provider instanceof IColorProvider) {
				IColorProvider colorProvider = (IColorProvider) provider;
				Color color = colorProvider.getBackground(anElement);
				if (color != null) {
					return color;
				}
			}
		}
		return null;