If I could, I would suggest giving a natural color pelleted food. The multi-colored stuff is nothing more than the equivalent of Fruit Loops that we feed our kids.
Sickness in our birds manifests "usually" in the poop first; but not always, if you feed m/c'd food it is a constant. That being said, various fruits and veggies can cause this too, but you would be quicker to say that after a couple of poops it will return to a more normal color/consistency.