Some films are better to be seen in black and white, it can add to the mood of the times that it was made in (depressed, broke or both!). Some of the Fred Astaire/Ginger Roger films in b&w look so classy and the Beatles Hard Days Night can only be in b&w. The change from black and white to technicolour worked really well in the Wizard of Oz but that was a fantasy film anyway. I don't think it works so well when it's attempted today not sure why that it is. Mel Brooks had a success with the Young Frankenstein the subject based on old Hammer type horror was going to make it more likely to be a success anyway.