Instructions
Run down the bridge that is directly in front of you when you start the level. Paint all of the lanterns that are along the bridge before heading back toward the opening projector.
Follow the green steps that have materialized at the end of the bridge. They will take you to the top of the waterfall.
Paint the paintable bridge at the top of the stairs and cross it to a secluded area at the crest of the waterfall.
Free the gremlin that is locked in a cage on top of the waterfall. He will be so grateful for your assistance that he will turn off the "thinner" waterfall, which will give you access to the riverbed.
Follow the riverbed all of the way to its end. Paint the bridge you find there and you will see the lantern on the other side of the bridge.