Stain over white paint???

I have plastic tile, that looks like ceramic tile on our kitchen walls. We do not want to take this off due to the expense in having to completely replaster the walls. Any suggestions on being able to paint over this? I think the texture of these tiles would look great, but in a different color than the lovely green. Gina

Am getting conflicting info about my exterior priming job. Rotting wood causes the need for replacing alot of panels. The wood panels have vertical grooves. The groves on the new panels don't seem to soak up the primer like the rest of the panel, the grooves are smooth and shiny unlike the rest of the panel. One individual says the groves don't necessarily need priming and doesn't really need to be that even on the rest of the wood, another person said it should be even coverage completely covering the entire surface including groves. Of course, it would be easier not to have the get deep into the grooves with the primer. Is it necessary for the primer to be completely uniform on the old and new wood?