Blue things can cause green poop. Plus sometimes it can be green from traveling too slowly through the digestive tract. I wouldn't decrease Creon because of constipation, it sounds like it would help, but it can actually make the poop even bulkier and pastier and make the constipation worse. It's counter-intuitive, I know, I tried the same thing. I believe one of the leading causes of bowel obstructions is not taking enzymes.
I'd adjust the Creon back to normal, increase fluids, and try something like Miralax if the constipation is ongoing. Fiber can help but in our case it made it worse, he was already so backed up, then we were giving him extra fiber which makes the stool even bulkier, we just got ourselves in a big mess. His GI doctor rec'd miralax because its not fiber, not a stimulant, and you don't have to worry about becoming dependant on it if you're taking it for a long period of time.