How long does a male have to have an std to have green discharge coming from his penis?

Not very long: Two of the most common stds are chlamydia & gonorrhea with incubation periods of 1-3 weeks & 2-10 days, respectively. See your pcp or urologist or infectious disease expert or an std clinic for diagnosis & treatment. Remember to complete all meds given, avoid sex until cured, & make certain all contacts r treated, too. May want to be screened for other stds: hpv, syphilis, herpes, hiv, hepatitis.