On cipro (ciprofloxacin) for prostatitis. However, blew green muscus out of my nostril/ how is this possible, while on cipro (ciprofloxacin)? Sinus infection? I have had a cold.

Green mucous. The color of mucous has more to do with the amount of moisture in your nose and sinuses and how recently you have blown your nose than it has to do with the presence of infection or not. Even if you had a sinus infection that was giving you green mucous, you will still have discolored mucous for a while after the germs are gone because it takes some time for any inflammation to go away.