Thanks, projectbluebird and PE for the clarification.
I may have been a bit too much into ultra-fine grain (Lippmann) emulsions - grain size < 30nm - which are completely transparent. Assuming two layers of the same type (same gelatin and same AgX concentration), you wouldn't see any internal reflections. One practical application might be coating a blue-green sensitive layer on top of a red sensitive layer. By the way thickness differences between the two layers wouldn't matter since the refractive index is the same.