Color does matter to some extent. Dark colors are just a pain to work with. Yes you are going to paint it, but it is much easier to work on a lighter, neutral, color than, say, black. Not that it is an issue here, but metallic plastic also sucks. Silver shows a black line where you cut and trim it, so it is really hard to tell if you have gotten rid of seams, etc.
As to passing off a new part for an original - the new parts are 100% identical to the originals since they come from the original mold. Only the name on the bottom of the base would be different. Since you are going to paint the model, it would not matter anyway.