Normally White balance is used to adjust the camera so that whites are truly white and other colors are accurate under whatever light source you are shooting. You can also use the White balance controls to deliberately introduce color casts into your image for interesting special effects.

Camera WB color temperatures are exactly backwards from the Kelvin scale we learned in school for star temperatures. Remember that a red giant star is cool, while a blue/white star is hot. The WB color temperatures are backwards because the WB system adds color to make up for a deficit of color in the original light of the subject.

For instance, under a fluorescent light, there is a deficit of blue, which makes the image appear greenish yellow. When blue is added, the image is balanced to a more normal appearance.

Another example might be shooting on a cloudy, overcast day. The ambient light could cause the image to look bluish if left unadjusted. The White balance control in your camera sees the cool color temperature and adds some red to warm the colors a bit. Normal camera WB on a cloudy, overcast day might be about 6000K.

Just remember that we use the real Kelvin temperature range in reverse and that red colors are considered warm while blue colors are cool. Even though this is backwards from what we were taught in school, it fits our situation better. To photographers, blue seems cool while red seems warm! Just don’t let your astronomer friends convince you otherwise.