Um, exactly what do you think they look like then? I have seen no evidence to the contrary that they are a type of dress/parade glove.
The ESB gloves are the Jedi gloves and are the prepro gloves-- same glove different painting/dyeing. Again, I believe the ROTJ are only slightly lighter in color than the ESB's due to washing and/or harsh conditions on set in the desert.
As for the helmet situation, you are seeing two different exhibits: one is the Magic of Myth (MoM) and the other is the Art of Star Wars (AoSW). The MoM suit has the Jedi helmet and Jedi suit. The AoSW has the Empire helmet and a Jedi suit that was also used for the Second Edition scenes.