I am in the process of restoring my dashboard and have started reassembly. I repainted the dash frame and now the plastic dash vents appearance doesn't look too good by comparison as they are quite faded. What I would like to know is, can the color (black) be restored by dying them or is my only option to paint them? I really would like to stay away from paint if possible as I fear the paint may flake off down the line after exposure to the sun. If they can be dyed, what type of dye would work best and if paint is my only option, what would be the best paint to use on them?

You could use a plastic polish on the vents. That will bring a shine back to the plastic. However, it's going to take a very long time to get into all the crevices.

I painted my Challenger center speaker cover with SEM Landau Black. I used their adhesion promoter after making sure the part was very very clean. I did the same thing to my Dart's dash vents.

They key to getting the Landau Black to look good is to spray multiple light coats. Just mist the paint on.