Hello I have a CLP-350 series PCL6 printer. When I turn it on, the display cycles through each of the colours at the top. Then it stops and the red light comes on and does not come off and the printer does not print. I believe this is happening because the toner is low. How do I confirm this and find out which toner to change? Is there a diagnostic to run? I'm using Windows 7 Thank-you.