Quantification of double IHC staining (purple and yellow )

I am running double staining with purple color and yellow color and blue for nucleus staining. My question is to find out if 1,there are more purple and yellows ( in terms of both positive cell number and staining intensity) in the treatment group than the control 2, if there are more co-expression in the treatment?
Can any one help me with that?

This question might be better addressed to the image analysis forum, image.sc. There you will reach people who are very knowledgeable about this kind of analysis. It will help to post some example images.