the green goop does indicate some some of infection or allergic reaction (could be dust, mold, pollen, something that he is allergic to and this is his eyes' way of protecting itself and clearing out the foreign matter). also lots of times shampoos in the eyes can cause this type of reaction. continue to use the antibiotic ointment for the eyes and i would wash them out with a warm cloth several times daily before applying the ointment. i see this alot at the shop where the water (soap, shampoo) during the dog's bath will irritate the eyes.
if he had a cold a few weeks ago, then i would bet he still has it to some degree or he is having nasal allergies.