Wait, you're going to talk about shaders next? I can see the interest if you are not going to use shaders and refuse to use any nodes at all. I guess. Maybe.

But if you are going to use shaders, why would you do this outside Poser then? All you got to do is connect the texture to an HSV node, choose a couple of appropriate parameters, and it's done. You can make any texture be any color tone you want directly in Poser. Many of the things Photoshop can do are built directly into Poser shader nodes.
 
For example, to convert straight to almost gray scale, set Saturation to .1 or similar really low values.

Then to make it more blue, do a Color_Math:Multiply with any shade of blue you like.

You can even animate this stuff so the color and saturation change over time.

I'm not trying to burst your bubble here, but this is a bit like telling people how to make horses go faster, and we're all using automobiles.

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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)