I want to share my complete approach to painting natural lighting in outdoor scenes, because outdoor light is more variable than indoor light and the rules need to be adaptive.

The dominant outdoor light sources: direct sun (warm, hard-edged shadows), cloudy sky (cool, soft diffuse light), golden hour (very warm orange-yellow direct light with long shadows), blue hour (near darkness, the remaining sky light is cool blue-purple), overcast (cool, directionless, lowest contrast).

For each condition I establish the dominant light color before painting anything. This becomes the top of my value scale. Then I establish the shadow fill color — the ambient light that reaches into shadow areas. This becomes the shadow value's hue.

Seasonal light: summer midday light is near-white with high color temperature. Winter light is lower in the sky, more amber even at midday, with longer shadows. The season affects both the light color and the shadow angles.

A practical tip that has helped me: look at shadow colors specifically when you're outside. Most people observe the lit surfaces and ignore the shadows. The shadows contain the most information about ambient light.