Overlap two images to emphasize their differences.

Hello, I am looking for a function that can solve what I'm trying to do.

I have two images saved in a folder, saved as jpeg. Let's call them A and B.

Both images A and B contain the same image, and they're the same size.

The only difference between them is that both have a yellow polygon drawn with roipoly in two different positions. What I would like to do is blend them together so that the final image C has both polygons in it, but not by adding them, because that would make the final image much brighter and I need to leave it with it's original colours.

Is there anything I can try?

Thank you!