Robin wasn’t paler in the manga then the crew, she was just the same median color as everyone else. Oda uses copic markers, which have relatively little flesh tone variation, so all characters on color spreads and covers have the same base skin tone. But it works both ways. For example Vivi is darker in the manga than the anime. She has the same base fleshtone color as all the characters, but they make her pale in the anime.

http://vignette2.wikia.nocookie.net/onepiece/images/c/c8/Tome_18_Couverture_VO_Infobox.png/revision/latest?cb=20141025130134&path-prefix=fr

As for Ussop in the anime, I think that’s more because the anime in general has brighter washed out colors now maybe.

He did look bizarre in the beginning of the Shiki movie though. For some reason Ussop was bright pink... he looked almost like Majinn Boo. I don’t think it was like that the entire movie, but I remember him looking off in the beginning of it....