So, what color is Storm's outfit, and why can't people agree on it?
In the late '80s, after Storm dropped her famous "punk" look, and while the team was operating out of the Australian Outback, she got a black leather outfit with tall boots, short gloves, "1980s businesslady jacket" shoulder pads, and a yellow lightning bolt on the chest.
To make it apparent that the costume was leather, it was drawn with white highlights to make it look shiny, which is a standard thing for comicbook art. (Look at how Longshot is drawn on that cover, for comparison.) Unfortunately, comics are produced on a tight deadline, so the more things you have to draw, the longer it takes; thus, as time went on, the solid black sections of the costume decreased and the white sections increased, to the point where she was often drawn like this:
Skipping over a few storylines (Storm gets turned into a child, the X-Men go to Genosha, the X-Men go to space, Muir Island Saga) we come to 1991's X-Men #1, where Jim Lee redesigned nearly everyone. Storm's new costume had tall boots, short gloves, "1990s pre-Image Comics" shoulder pads, and a straight yellow stripe down the chest - far from a major departure, it must be said. And notice that he drew it like this:
Nearly identical to the way the old black suit had been drawn. Therefore, fans who had been into the comics for a while "read" it as another black costume; but the thousands of new fans who picked up the book weren't pulling from that same visual library, and thus when they saw the same costume, they saw white.
It's clear Jim Lee intended Storm's new costume to be black - one need only look at the trading cards released concurrently (keeping in mind that Impel, the company producing the cards, was a Marvel subsidiary and thus privy to access and information beyond what was on the printed page). Being printed on different stock and with different inks meant a wider range of colors was available. And without fail, every "outside the comics" appearance of Storm at the time definitely showed her wearing black. Or at least a dark grey passing for black.
But here's the thing. At the time, the X-Men were divided into two strike forces: the Blue Team in X-Men, and the Gold Team in Uncanny. Storm was on the Gold Team, so she wasn't in Jim Lee's book, meaning he wasn't her primary artist. Whilce Portacio handled the chores there, and while he and Lee worked fairly close together, it meant Jim wasn't the final arbiter of her look. So if a colorist decided to make the suit a little lighter one month, Lee wouldn't be there to say that was wrong. And if it happened again the next month, and the next month... well, soon enough both artists yeeted away to found Image, and new pencillers stepped in, merely copying what they thought they'd been seeing, and eventually Storm was being specifically drawn wearing white.
(The cartoon didn't use true white for anything other than the barest highlights, so there she ended up wearing a light blue that many took for silver - but it's the same color as her hair, so make of that what you will.)
The shift from black-with-white-highlights to white-with-black-shadows was a slow one, an incremental one. And frankly, even the books themselves couldn't decide what color the costume was supposed to be, with it being depicted white, black, and various greys or silvers right up until the Onslaught story, where she finally changed it. Jim Lee may have intended the costume to be black, but it was absolutely shown pretty much everywhere on the black/white spectrum, so whatever shade you personally think it is, you're probably right.
But really, considering it came out of the early '90s, wouldn't it make sense that it's made out of that shiny white rainbow material that was all the rage at the time?
Imagine how cool it'd look when lightning flashed off it!