Desaturate most but not all materials?

I would like for some actors in my level to stand out a little bit, without resorting to glowing effects. I wonder if it is possible to have a post process on the camera which does something like tint or desaturate the view, but has no effect, or the opposite effect, on a certain material?

I’m open to other ideas as well… I just want some items to visually stand out.

You’d have to put some work in adding a material function probably or something like that to all your materials, but then maybe using a Material Parameter Collection controlled from some ‘Look Actor’ or something could let you manipulate many shaders at the same time.

EDIT: How about doing it with a bit of extra lighting? Linked to only the character(s)? (using the channels)
You could maybe have a light function that blended those lights in from the legs up, so that he/she would still blend into the envirnoment. (not tried)

Cheers

You could put the objects you don’t want to desaturate in a custom depth pass, and use it to mask out the desaturation in your post process.