Notice the orange to green to purple gradient in the river. This was caused by the orange sodium light cast from the parking lot at the top of the falls. The natural green hue of the water shows through in the middle from multiple (neutral white) flashes. And the purple color cast from the hand-held flashlight is only visible nearest the camera as it was the weakest light source and had a different color temperature than the strobe.
Pretty neat to see all the light sources and varied color temperatures work out like this in a single shot
Info: F/5 | 30.0s | ISO 125 | Flash Did Not Fire | Canon EOS 50D | Lens: EF-S 18-55mm