My most recent assignment is to use a variety of color temperatures (AKA white balance) when capturing subjects. In a film camera you would achieve this result by using a filter over your lense, which changes the tonal value of the image. In either digital or film photography, adjusting the color temperature can give you some pretty interesting results.
The color wheel (not the one you learned in high school, which I've come to understand is very simplistic and inaccurate) is the bible to counteracting and enhancing colors and tonal casts. For example: green counteracts magenta (Trivia: Magenta doesn't exist in the spectrum--you'll never see it in a rainbow); cyan absorbs red; and, yellow cancels out blue. This color wheel, which I have to admit I am utterly fascinated by, is very different in that red doesn't cancel out green, blue doesn't cancel out orange, nor does yellow cancel out violet, which is what the color wheel we were taught in beginning art class indicates. I've never really been a theory person, but I love color theory! Todd Manville, (he's my brother-in-law) Master Printer, Sage of the Press, I bet you could teach me a thing or two about CMYK (cyan, magenta, yellow, and black)--maybe if your father-in-law, or wife (yes that's a link) read this they'll let you know that I want some of your know how, oh grasshopper of the printing world.
Side note: Some of you blondes use color canceling on a daily basis, in the shower. Yellow and orange are cancelled out by violet and blue, which is why you use a blue violet shampoo after a foil that leaves you brassy.
The below photos illustrate how adjusting color temperature can change the mood of a subject. I chose to photograph out my office window for a couple of reasons: 1. It's convienient 2.The building I look onto is a very neutral beige and there for a good canvas.
If you want to laugh, take a closer look at the person in the rolodex. :)