So then, in most of the publicity and behind the scenes stills of the TMP spacewalk that I have, Spock and Kirk are wearing completely different spacesuits than the ones they wear actually in the film. These suits can be seen hanging up in glass units as Spock enters the airlock bay and nerve-pinches the technician.
The actual suits that Kirk and Spock wear are the Wrath of Khan suits minus chest handles.
Scarecrow's back and asking about costume details. I'm excited
But to answer your question, I have no idea. Maybe the suits used in the publicity stills were made by the effects house that got fired (was it Brick Price ?) and weren't considered of high enough quality for close up work.
The suits were indeed from the early shots done by Robert Abel and Associates, and were replaced by the coloured versions. If you look at the original VHS release of the movie, you'll see that the inserted some footage in the video using the early suits - and missing matte shots - where Kirk goes out to follow Spock. I'm given to believe that they eliminated this for the DVD "Director's Edition."
BTW, Brick Price was not dropped from the production when Abel sna Associates were, they did a lot of prop work for the movie including the PADDs, the "Perscan" belt buckles, Type II Phasers and others.