Metallic colors are next to tough to Photoshop. They are very reflective, and get most the look because of it.
Personally, I think your best bet is to Google the colors you are looking for. You can get a very good idea of what it is going to look like, even if it is not specifically on a Fiero.
(These images are 'hot linked" so not sure if they will work, or how long they will last if they do)
For instance here is the Flat Blue metallic:
And the Flat Metallic red: