Just assume that on their last mission that they were so far out that they never got the new uniforms. Their 5 year mission lasted the entire time that those uniforms were in use, so by the time they're back, the new red jacket model is in. Then their ship is due for a refit. It shouldn't take too long after getting it right with the new Enterprise, but let them have a shakedown cruise, and make comments like "it's not like the old ship". Even if the refit improves the ship, the crew may still prefer the "way it was".
"Retreat?! Hell, we just got here!", annonymous American Marine, WWI
"Gravity is a harsh mistress....", The Tick