If you go to the website and look at the original image of the lounge (and there's a few different ones) and enlarge it you can see there's color on the screen in the faces of the people. But, back then doctors and nurses wore gray and the walls were gray, so there's not much color to begin with.

Also, I wonder if the lighting was a factor. Those old TK-41's needed very bright light. The camera in the operating room doesn't have the lights mounted on like the one in the dentist room. I supposed the doctors didn't want bright tv lights glaring in their eyes while trying to perform surgery.