Although it looks grey in that photo, in live action, because it is so dark, it really barely looks grey at all. It blends in so much with the rest of the costume that it practically looks monotone at times. I remember when she was fighting AOS's version of Whiplash, Marcus Scarlotti, and Bobbi's uniform really didn't look any different from the other standard SHIELD outfits.
Surely they could've had it an open jacket, which could be zipped up at times, and Bobbi could've worn a white shirt under it. That way, if she wanted to go into stealth mode, she could zip it up, but the rest of the time she would prefer to wear it open, exposing the white top underneath. Then we would've had a more comic accurate look, and people who complain that white doesn't work for stealth wouldn't be able to complain, because she could just zip it up when needed.