Coloured Restrooms

I've read somewhere that for the sake of drama, a lot was exaggerated - the bathroom scene included.
IIRC, there actually were segregated bathrooms at NASA, but the black worker (I'm blanking out on her name) used the "white" bathroom in the building without much fuss.

NASA was one of the first entities to do away with that bullcrap of "separate but equal," because they couldn't afford to have something as stupid as that get in the way of conquering space. The last thing they needed was to inconvenience their top technicians and mathematicians because of some stupid laws made by Southern Democraps as a substitute for keeping black people down when slavery laws weren't legal anymore.

The film covers dates that spanned NACA and NASA agencies early times. When NACA was expanding during and after WWII, they had to comply with the obscene segregation laws of Virginia even though they were a federal agency. So yes, they had white and colored restroom.

Costner's character (fictional) most likely did not have anything to do with removing any colored bathroom signs. Even then, how they did it in the film was stupid. It should have shown him removing the "white women" signs instead.

The book Hidden Figures does have several amusing anecdotes about the women resisting the stupid segregation rules. Miriam Mann kept on stealing the "colored computors" signs in the back of the cafeteria; it was her way of protesting. Eventually the signs were not replaced.

Katherine Johnson used the white women restrooms when she was transferred to work directly with the engineers because she did not know of any other restrooms. When she learned that she was to be using the colored restrooms only, she ignored the rule and no one ever complained.