public void setProblemRowGradient(String colorName) throws Exception {
		if (colorName == null) {
			lock();
			problemRowGradient = null;
			problemRowGradientName = null;
			unlock();
		}
		else {
			Color color = selectColor(colorName);
			if (color == null)
				throw new Exception("Color " + colorName + " is not known.");
			lock();
			problemRowGradient = color;
			problemRowGradientName = colorName;
			unlock();
		}
	}