Yes, all the Troughton restorations are in their original B&W, but i am sure i remember a few Pertwee restoration dvds that had the odd B&W mixed in with the colour episodes, and i can't remember the reason given on the extras, as they were quite good at taking found episodes from around the world and fixing them right up, but no doubt money might have been one of the facts as over the years it was touch and go at times for them to continue restoring the show.
Oh and not to go too far off topic when it comes to restoring old UK shows, i just found out a restoration of the 70s cop show The Sweeny has been completed and is about to release on BR, now if only someone would go and restore the Will Hay movies, then we will be sorted.