It's pretty simple. The Enterprise and the other Constitution-class starships were designed and built by a different contractor, so they have different design elements from the other ships we see in DSC. The interiors, including the multi-colored uniforms, control surfaces and decor, are part of a Starfleet psychological experiment that people on stressful, deep space missions would perform better and be happier in bright, colorful environments. Given the long-range 5-year missions of the Constitutions, Starfleet figured they'd give this a try. There's absolutely nothing anywhere that says that Starfleet technology looks the same everywhere all the time within an era.
As someone mentioned on a different thread (and I've actually said in the past as well)...baldness is just "in" amongst the Klingons in the 2250's. It's feathered hair in the 80's or grunge music in the 90's...an intense but very passing fad.
See how easy that was? No need for a visual reboot or an aneurism about the design choices of the show and all that. It's just like saying that Chekov was on 3rd shift in Engineering during Space Seed, and that's how Khan must have known him. If we can make up inane excuses for other inconsistencies in Trek...I'm sure we can all do the same now.
Simple, simple stuff, folks. How 'bout y'all just go with it and be happy, huh?