I changed my panels from one blue and one teal to both red.

I washed them thoroughly in warm soapy water and scrubbed them with a soft bristle brush. After that I used a good wax and grease remover (PPG), used Dupli-color's adhesion promotor and then Dupli-color's red.

I purposely tried to scratch off the red after everything was dry. It wouldn't come off! Looks and worked really good!