Common place in comic and older media. Mainly used with hair.
So you're looking at a series. It's in Black-and-White, but you can guess the colors of the characters. Maybe that guy has black hair, you think. But when you look at the officially colored works their color is a dark brown. Or maybe that one girl has blond hair when apparently she's really a brunette.
- Pokémon Special occasionally suffer from this. Black and White have their game hair colors, though White's is somewhat lighter then the vaguely-brunette Hilda. However their shading in the manga is a black shade, used for the raven haired characters.
- Wandering Son used to feature this in the first four volumes. Characters like Takatsuki and the Nitori siblings parents all had brown hair in colored work but their shading implied black. Eventually they were retconned into having black hair.
- Junichirou's hair from Boku to Boku is a light shade of black but his shading suggests a much lighter tone. Similarly another character has bright red hair when their shading implies a dark tone.
- Naruto has Karin, who has red hair, but it is depicted as black in the black-and-white pages.
- Harpo Marx's hair went from very dark to very light (practically white) during his B&W film career, but it was always supposed to be red - and it was red in live appearances.
- Donald Duck's blue sailor suit is often painted black on old comic books.
- Triela has brown skin in Gunslinger Girl but her skin wasn't shaded correctly for much of the run so she often looked just barely darker than the other characters, if not as light. Eventually it was cleared up though if anything her skin tone became darker than in colored artwork.