The RH96 predates the XT scanners by some years. In fact, there is a firmware update for the RH96 to make it compatible with the XT scanners. That doe NOT include adding colors to the remote head, but I believe that to be a hardware, not firmware controlled item.
The RH96 was "discontinued" a few years ago because of poor sales. New ones are occasionally built and released using existing stock, but Uniden doesn't seem interested in releasing a newer version.