Are there apps to train your eye for white balance and color temperature?

With experience you become more aware as to how lighting and the color of the illuminant will change the way a vista will reproduce. You begin to see that shadows on snow have a blueish tint and you become aware that tungsten lighting is biased towards the yellow.

We humans see with our eye/brain and that complicates. Try this enlightening experiment. Procure some strong colored filters, you know, deep red, strong yellow, strong green. No filters? OK, colored transparent cellophane candy wrappers etc.

Now hold one of the strong filters before just one eye. Look about keeping one eye is strongly filtered, the other not. After about two or three minutes, remove the filter and look about. You will find that the color balance of the filtered eye is quite different than the unfiltered eye. This demonstrates how the eye/brain combination effects color vision. All day long, as you move from place to place and anytime the color of the illuminant changes, your perception of color changes.

What happens is, the color receptors on the retina change their sensitivity. In other words, the eye/brain attempts to adjust the lighting condition to “normal”. You are unaware because it happens simultaneously to both eyes. In this experiment only one eye is changed; thus you become aware of the magnitude of this phenomenon.

Do perform this experiment; it will help you understand white balance.

I suggest you read "Color As Seen And Photographed" an out of print Kodak publication E-74