Highlighting Stencil Mask Pixels

I'm using stencil masks to look through portals into other scenes and I'm trying to figure out how to modify the final pixel color of the stenciled pixels. Currently I have 2 passes set up, one that sets the stencil buffer and another that clears the depth buffer (per this thread). Is a 3rd pass on the stencil mask the way to go? I quickly tried it and am not getting any color changes. Any ideas?

E.g. - want to be able to tint the final pixel color inside the box here

 

Yes, a third "pass" would be the way to go. More specifically a separate material that renders at a later queue, otherwise the other objects will just render over it as if it's just a third pass later rendered objects will always render on top.