It became popular in the 80s and on through to the modern age to make changes in costumes fairly regularly, even if they usually end up reverting to the original design eventually.
But I've been thinking about some of the fairly big changes that Marvel made in costumes during the Silver Age lately.
I think Iron Man and Daredevil are the two best examples. Daredevil went from the black and yellow costume to all red, something I think most consider to be a positive change.
For Iron Man it made sense to occasionally update the armor. He started out with the bulky grey, which quickly changed to gold. Then the armor was streamlined and went through a few other changes until it arrived at the design that was used throughout the 70s and much of the 80s. Again, this is something that made sense and I think these are generally viewed as positive changes.
One negative change that occurs to me was Roy Thomas and Gene Colan's Dr. Strange revamp. We went from the wonderful and unique Ditko design to a faceless version of Strange with a more super hero themed costume. I have always intensely disliked this look, and still don't really know what Roy and Gene were thinking, unless they were trying to associate Doctor Strange more with super hero fans. Very poor design choice.
So what are some other early Marvel costume changes, good and bad? And which ones ended up sticking?