There are many circumstances under which you might want to override your camera's auto white balance setting. For instance, often you'll shoot a series of photos to document an event, such as a birthday party or wedding. On the auto setting, the camera will make its best guess with each exposure. It's likely that the camera will choose a slightly different white balance with each exposure. When you look through the photos later, skin tones might look OK in some and too yellow in others. To prevent that from happening, it's better to select one of the preset white balance modes on the camera. Most come with settings for tungsten (indoor lighting), flash, sunlight, and cloud cover. Select the one most appropriate for the circumstances. Don't be afraid to experiment and pick the one that looks the most accurate to your eyes.
You can also use white balance settings to achieve special effects. For instance, I used a custom white balance to turn my flash color blue in this photo of Chelsea for Incendiary Circus. (Figure 3)
White balance can also be used to intentionally modify the color hues that make up an image. For instance, both of these photos were taken in the same place, with the same background, under the same light (Fig 4 and Fig 5).
With the latest digital cameras, the Auto White Balance is good for general lighting. But when you need something special, don’t be afraid to take it off Auto.