Not all of the time, but some of the time, the X-Men's costumes seem to be color-coordinated, and/or share similar designs. It can be argued that it makes sense for a team to have uniforms that are... ya know... uniform, but it can also be visually uninteresting. I've never read the original original X-books, but along with the fact that the entire team was for the most part a bunch whitebread dudes, all of their costumes looked alike. Angel had wings, and Beast eventually got furry, but, aside from Iceman obviously, they kind of looked boring. I think a lot of the appeal of the post-Giant-Size X-Men was that they were so different: different nationalities, Nightcrawler's and Colossus' distinctive appearances, more diverse personalities, AND they had such colorful, unique costumes. They were in no way interchangeable, and the extreme visual differences added a lot to that, at least subconsciously. With a series supposedly about accepting diversity that approach made a lot of sense. It seemed to be the same way all the way up to the 2000s (please correct me if I'm wrong), and all of a sudden they went back to uniforms that mostly looked alike. I could be wrong, but besides Storm and Beast, who were always mainstays, the number of visually distinctive X-Men also seemed to drop to an extent.
Now I see Uncanny X-Men, All-New X-Men, and a lot of the other titles, and there's still a lot of the same costumes and whitebread characters. It's understandable with All-New, since it's actually about the original X-Men, but still... And Uncanny seems to be the worst offender. Sometimes I confuse Emma and Magik, then there's the Stepford Cuckoos, they all look totally human, and aside from the healer guy, the minorities are pale enough to be mistaken for white half the time. (This isn't an issue with racial diversity, I'm just talking about visual diversity.) Although the boring characters don't help.
That's something I liked about Uncanny Avengers: the costumes are totally different and it helps to illustrate the wildly different characters. Granted, they're a team divided, and that was kind of the same dynamic as the post-Giant-Size X-Men team, but I'd still like to see costumes that are more interesting and really make the individual characters stand out more.