Your camera’s white balance function compensates for the variations in color temperature by making the dominant colored light appear as normal white light regardless of its true color.
When a camera has not been properly white-balanced, sunlit scenes look hideously blue or indoor scenes look horribly orange. Most cameras have built-in preset functions for daylight and indoor white balance and fairly reliable auto-white balance (AWB) functions. Use these presets or auto if you like the look, but if you want to shoot like the pros, there’s only one way to go. . . manual.
When to White Balance
You should always white balance anytime the lighting conditions change, such as the sun is lower in the sky or you turned on some overhead fluorescent lights. A good example of this is capturing a football game where starting out in sunlight and ending under stadium lighting. If you even think the lighting conditions may have changed, you should re-white balance just to be sure. Remember to white balance before adding gels to your lights or your white balance will not be correct. You should use pure white cards or standard bright white paper for normal white balancing. (A crisp white T-shirt will also do in a pinch.) Avoid using off-white and cream-colored paper to white balance.
White Balance Special Effects
White-balancing on colored cards will produce different looks. The cooler the color you white-balance to, the warmer the look and vice versa. Unless you’re sure you like the look, it’s better to do color effects in post, because you’re pretty much stuck with that look once you white balance and it’s nearly impossible to restore a normal white balance after the fact.
Mixed Sun and Indoor Lighting
When shooting in mixed lighting sources you can white-balance normally to split the difference or you can gel either light source to match the other. Color temperature orange (CTO) gels are used to make daylight appear as indoor (tungsten) light. Color temperature blue (CTB) gels are used to make indoor light appear the same temperature as daylight.