Wrong colours? Wrong white balance…
If you notice a colour cast on your images when you preview them, the chances are that the wrong white balance has been set. Most photographers leave the white balance in its Auto setting, and with good reason: it generally does a decent job of removing colour casts and providing natural-looking results. It can remove some of the character of the light, though, leaching some of the warmth from a sunset shot, for example, and it can also get things wrong under artificial lighting, too.
Auto white balance can also change the colour temperature from shot to shot without the lighting changing very much at all. This can cause problems if you decide to batch-convert a series of shots from the same location, as each image may have to be tweaked individually. To ensure consistency, and speed up your digital workflow, it’s worth switching to one of the manual presets, creating a custom white balance or dialling in the colour temperature manually.
Use Live View to preview the effect that changing the white balance has on an image