Counting cells in stacked image: Only count cells which show both stainings

[endenoi]

Hi all

I have an image containing Dapi staining (i.e. for cell nucleus staining: blue) as well as an image showing a rhod staining (--> in order to visualize beta cells of pancreatic islands: red); I do know how to count the respective colored areas in each of the respective pictures,- but I have a hard time figuring out, how to count the ones which show both stainings, i.e. when I merge the two pictures together. Therefore my questions would be:

Is there a way, to count only the cells which fulfill both criterias, i.e. both stainings (blue and red) as I merge the channels?

It would be very helpful if I could get this to work, since I have an enormous amount of images to count otherwise by hand. I'm thankful for any hints!