The ultimatel shadow lesson

[eddieooo]

So let's say we have a blue sky green grass then on a sunny yellow day the shadow of a tree on the grass is purple (complement to yellow) . But if the day is purple like twilite then the compliment of purple would be a golly Lellow shadow do you agree the shadow is the compliment of the light's color ?

[querin]

As yellow is too light a color in this instace i would use the color next to the color wheel complimentary and use Pthalo green to shadow purple.
querin

[virgil carter]

Eddieooo, the color, saturation and edges of shadows may be determined by some of the following criteria:

• The color and temperature of the ambient illumination, which affects the color of everything
• The strength or weakness of the ambient illumination
• The color of the element(s) on which the shadow falls
• The color of reflections from near objects
• The complementary color of the object throwing the shadow
• The saturation and edges of shadows, which are stronger closer to the object casting the shadow
• Combinations of the above

In your example, the illumination (twilight) is weak and cool, thus your shadow's saturation, value, edges and temperature will follow suit. As to color, I'd use the criteria above to select a shadow color harmonious with the rest of the painting.

One thing's for sure, as you describe: shadows are never opaque, never black and never a "universal" color, ie, Shadow Green, etc. To verify, just step outdoors and observe a shadow!

Post what you finally select.

Sling paint!
Virgil