Let's say I have two layers with some black pixels on them:
What can I do with blending, masks, knockouts, etc, such that when these two black things overlap, they reveal the color underneath, like this?:
I accomplished the above with a jury-rigged technique of manually creating a white duplicate of one of the shapes and using a layer mask to reveal it in the right spot. What I'd like is a more streamlined way that doesn't need an additional pixel layer, and can keep the knockout effect as the two shapes are repositioned.