White balance adjustment tool.
I forgot to include in the article below (Shoot RAW for better color) a handy tool for estimating the correct white balance when different light sources are involved, like a room with warm tungstenlight along with some cool outside light coming from nearby windows. I have the 77mm neutral xpodisc, and find it works very well in getting the colors in the image very close to what they’re supposed to be, and is quick to install and remove.
If you have plenty of time, you can play with manual color temperature adjustments, (and green/magenta shifts) and work your way shot-after-shot to the correct color by eye, if you don’t know how to do that, the expodisc will make it a lot easier.
If you decide to try one, I’d suggest the 77mm, that way you can use it on almost all lenses. It lightly snaps on the lens front filter threads, but doesn’t screw on. If your lens has a smaller diameter filter size, just hold the expodisc up to the lens and go from there. You use your camera’s custom white balance setting with the expodisc installed to figure the correct white balance.