Gels are just pretty darn cool. I've only recently begun really playing around with them, but you can do a whole heck of a lot more than merely color correct for tungsten or fluorescent ambient lighting.
The other night I was feeling the itch to mess around strobist style and setup and umbrella and grabbed my gels that have been mostly sitting unused in my lighting bag. Towards the end of my session of too many bad self-portraits I decided to have a little fun and see what I could accomplish. I put a Storaro Red on the umbrella strobe at camera right and set up another flash behind me on the floor pointed back at the grey backdrop with a full cut of Color Temp Blue. I also put a gobo on the flash so none of the blue would wash onto my back.
This is the untouched result other than cropped and EV boosted by 1/3rd stop in LightZone and then resized for posting.
And yes, I need a better looking model...
