Click here for examples of Four Horsemen Prototypes.
Just find a figure you have (that also has a prototype picture) and compare them! You'll get the gist of what changes between proto and finished product. Most of the time, the paint will look different, because either A) the plastic will be molded in color rather than painted, or B) the paint looks different on finished plastic than it does on the resin that the prototype is made of.
Granted, I know this doesn't answer your question completely, but since we won't see the finished product for awhile, this can give you an idea.