White balance

What is white?

Technically there is no white color. If you have light from all of the spectrum equally, you do not see individual colors, but a fully saturated mixture, which we call white. But what is the mixture of colors that gives you the real white.

What mixture gives white

If you remember the discussion about light, the problem is not the color of the objects, they always stay the same, but the light that is illuminating the object. If you have one of the kinky red lights in your room, everything will be red and black. You will have no yellows, purples or also white. We call such light that has only one 'color' monochromatic.
If there is a more natural light source (sunlight, light bulb, LED), you will have a different spectrum (or color components)
If you are talking in RGB terms (where every color is represented by the fraction of the colors Red, Green and Blue they contain), white will be maximum red, maximum green and maximum blue.
The problem is to figure out how you want the colors interpreted, if your light does not exactly have the daylight from sun. The white balance basically accounts for the fact that your light source is slightly different, and the mixture that gives us the white is not as we expect it to be. Maybe it is a bit more red, blue or green, once you know how the color components from your scene under the light you observe come together, you may be able to tweak the mixture, so you see the colors as you perceive them.
Most cameras will try to figure out this mixture and automatically correct (Auto white balance). The problem is if this mixture is not really correct, you can add either a correction term or tell the camera what the mixture is.
The simplest auto correction is, to point the camera to something that you know is white.

Simple tips

Fixing the color in post-processing is actually very common. Technically there is not much difference between fiddling with the light (environment), the controls on your camera or adjusting it in post-processing.
In some museums, the spot light will have their color temperature written on them. By the way, bright daylight is about 6000K
In complex conditions where you can not seem to get the white balance right is simply to go black and white.

These pages are for Amateur Photographers and not really for seasoned photographers and professionals. I have no affiliation or commercial interest with any brand/make. I write from my own experience. I ended up using mainly Nikon, so I am more familiar with this brand than others. See price for notes on pricing as well as photography related links.