Measure distance between two types of proteins' stains

Hi,
Attached are two images of different proteins, each stained in a different color (Gfap in green and ABeta in red).
I was wondering how I can measure the distance of a green object to a red object.

At the end I want to be able to show the distribution of the shortest distances between the two types of proteins, so for that I need to find:
for each object in the green image - it’s closest neighbour in the red image (and vice versa).

Thanks
Shimmy

Your question will make more sense when you define what is that you call an “object”.