Well, the color of the poop can vary depending on what they eat. I have seen the following types of poop from my turtle:
olive brown logs - Reptomin pellets
flaky olive-brown pieces - romaine lettuce
pinkish-white logs - salmon
dark brown, almost black - blueberries
What brand of pellets are you feeding them? I hate to make you post a picture, but that may help us understand what's going on better too.
