Jay P. Morgan of The Slanted Lens is one of the more energetic and therefore entertaining characters in the photography world. His videos are usually a good mix of oddball antics and solid educational material. In this video, Morgan demonstrates how simply swapping gels on your rim light (with a bit of haze in the air) can really change the feel of your photo. I'm usually not a huge fan of fake smoke or haze machines, as I think they can look a little overdramatic and cheesy. However, I think it works in this instance, because he uses a subtle touch of haze, and it fits with the subject matter.
Using Roscoe 12x12 gels, Morgan can easily cover his light, a Dynalite Baja, (which by the way is an incredible internal battery monolight). It takes a bit of experimenting to see which color and which strength looks the best, but luckily, changing the gels is quick and easy. If you've been shooting with off-camera lighting for any amount of time, gels are likely old news to you. However, if you've just begun delving into this realm, the use of gels can be an exciting discovery.