Occasionally, green, mucous-like poop can be caused due to viruses that can include fever, diarrhea. This description looks like the poop in the picture you've attached. That being said, since your baby just recovered, I reckon the poop will stay that way till baby has fully regained health.
Don't worry too much, keep baby hydrated and when baby is up to it, keep his strength up by giving him bland purees. I hope your baby gets well soon!
http://www.webmd.com/parenting/baby/features/truth-about-baby-poop?page=3
Janice Tan