John Mason wrote:
starfleet had already made the transition to the new uniforms when Voyager put to space.... either that or Bob Blackman decided on a larger wardrobe....
Actually, here's what happened. New uniforms were made for Generations, but ended up ultimately not being used, as the producers didn't want too many changes from TNG (although they instead had the crew change from the TNG uniforms to the DS9 uniforms halfway through the movie, which was even more awkward than having new uniforms right from the start
Playmates actually released an action figure line with the TNG crew wearing the new uniforms, based on concept art:
Pic of an actual unused uniform:
These new uniforms were what the crew of Voyager were supposed to wear, but because they were never used in the film, and the DS9 uniforms were, that's what they ended up using on VOY.