I think that this is what's happening. But again, I don't see why Photoshop can't just replace a color you select by another color you select, setting the fuzziness and stuff.
It has sense that light colors get replaced by light colors, but if a user don't want to preserve these lights and shadows of the original photo, the "Replace color..." tool should provide a real "replace this color by this color" solution.
OK, that kind of explains one of the problems.
But, what about the second one? Try to replace the black jacket color by a red one. You get some weird colors all over the picture. I still don't understand that. I've faced dozens of times this issue: I wanted to replace a white area or a black area of a picture, and never could with this tool. Even solid areas, where there was a pure black right there.
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OK, Sam, I was working on the picture, but in the minute 3:20 of the first part, you painted black all the jacket, removing the original texture of it and its bends (next to the white T-shirt). Can I leave that as it is?
Thank you!