I'm new to this too but I can share your pain with the diarrhea and liquid diet. I had two weeks of liquids before my surgery and a week of clear liquids post op. Now i'm on a week of full liquids and do mushy foods next week. I researched what I could possibly be pooping after almost a month of nothing. I'm not sure how accurate this is but it makes sense so I'll share it with you.
Urine is the liquids that have been flushed from your bloodstream. Any extra liquid stays in the colon. We're on liquid diets thats explains the watery stool. In addition, anything you drink that is not Water has particulates that are broken down in the colon. That's why there's always a little something besides water. Also, your body dumps waste (dead cells, etc) in your colon, too.
Lastly, the water is a brownish/green/yellow because your liver is releasing bile making it that color.
Hope that makes you feel a little better. Congrats on your band! We're band buddies, I was banded April 11.