Here is another tree with a lesson inscribed on it. Look at the body, or the middle of the foliage. On the left it is that deep green and on the right it is a still darker more violet green. The leaves themselves are of course really the same color. They are different colors and values because of the different sorts of light hitting them. The very green leaves over on the left hand side are being illuminated by reflected light. That is coming from the brightly lit field.
The leaves to their right are in the core shadow. They are the least illuminated part of the tree and receive little light. There are branches sticking out into the light in the middle of the tree, these are receiving light from the sky above, as the tree is somewhat top lit. Top light is usually going to happen in the middle of the day and is generally the least desirable working light in the landscape incidentally. These top light areas are high in value and they are influenced by the color of the sky reflecting in them, particularly in their high lights. The reflected lights are where the leaves act almost as little mirrors positioned in such a way as to turn the sun light and send it directly at you. Highlights in particular tend to be tinged with the reflected color of the sky.
The top of the tree is in the light and is influenced by the color of the light. The more a passage reflects the nature of the light, the brighter it will appear. That is, as the object is increasingly illuminated, the local color and value of the object will decrease and the color of the light and its value will replace them. Although it is not apparent in this photo it is often useful to introduce a reflected sky color as the tree turns over on its top. That is where the planes of the tree are no longer on the side, and facing you, but on the top and facing the sky. Cooling the top of a tree like that will make it "go over", that is, it will seem to round as its form turns up and out of our sight on its way to the other side of the tree. (gee, I hope that made sense).
Often the trunk will be full of reflected light from the ground. This is important because it ties the tree into the same world as the ground. This small percentage of shared color keeps the tree and the ground in the same tonal equation. If there is no common or ambient tonality in a painting it can become a mosaic of unrelated color. And you don't want that.