1x11 - The Adventures of Teddy Ruxpin

Teddy and Grubby run into a group of Fobs who have lost their color. This leads them to enlist Wooly to climb to the top of Rainbow Falls, where he finds a boulder blocking the water where it runs from a cave. Wooly removes the rock, and the water resumes flowing. The Fobs drink the water, and get their color back.