The characters with the gray look are using shaders that have a blue tint on the Diffuse-Color. This tint is not a good idea with gamma correction enabled, and is a leftover skin shader technique that never should have been copied, but got copied a lot. The first thing you could do is set all those to white.

But ...

You should be using a skin shader with scatter. Use EZSkin and just replace the shader altogether with that.

The other advice regarding setting gamma to 1 on bump, transparency, and other non-color maps is correct but totally has nothing to do with your problem.

Or - you could turn of gamma correction, but then you might as well not have upgraded.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)