I think I achieved something that you can use to a small degree. At least it is more than enough for me.
I get zero credits as most of I have done was copy pasting and testing on what is best for me.
Here is a scene where you can change the color of the whole map but not the mesh that is blue, which has depth buffer on.
When you create this Post Process material, make sure to make an instance of it “Create Material Instance” by right clicking over the material. Then add it to Post Process Box’s Blendable property section. In the instance, you can change the color all you want.
Also don’t forget to check this one on your meshes that you want them to be excluded from post process effect.
Note that changes at your post process box will STILL effect this mesh. I have yet to find out how to prevent that, but for now, my own solution is enough for me, and you may want to fiddle more for your own needs. Good luck!