What makes long greenish feces?

Stools. Color is related to amount of bile produced in your gallbladder. Consult a gastroenterologist if stools are colorless, black, or u r having other symptoms.
Transit time. Eating green leafy vegetables can lead to green stool. Green cabbage, lettuce, peas, cabbage, spinach, broccoli, green salad, green leaves, celery and green beans as well as food that contains green food coloring can lead to green stool. If the stool was loose, the reason for green stool could be too rapid a transit time in the gut.