I'm confused by your confusion. You always have two choices: uses the presets correctly, or white balance for the scene. To use the presets, if you are shooting in daylight or with daylight-balanced lights, set the preset to daylight. If you are shooting inside with tungsten lights, set it to tungsten. Pretty straight forward.
Note my post on the "greenish tint" thread (
http://forums.creativecow.net/readpost/47/856931) for a brief overview of the blue-red color axis and the magenta-green color axis.
Rick Wise
director of photography
and custom lighting design
Oakland, CA
http://www.RickWiseDP.com
http://www.linkedin.com/in/rwise
email: Rick@RickWiseDP.com