As a painter, most of the technical details are lost on me, though I get the gist.
Looking at the results, it seems that the author defines a base color (green for the leaves) and moves up and down in brightness using what amounts to a multiplication for the shadows and an add for the lights. The result feels a bit harsh and unnatural.
I would suggest that he also plays a bit with the hue values.
1. That he darkens the lights but moves the green towards yellow.
2. That he lightens the darks, but moves the green towards blue.
As a programmer who dabbles in painting, what you are describing is indirect lighting and subsurface scattering (leaves are sort of transparent, so from the back they look yellowish, and the sky is blue, so shadows have some blue in them).
In a full rendering pipeline (not the simplified one just for the effect) this would already be implemented, but it's a good thing to remember.
To be fair to the (epic) work of the author, a spacecraft likely wouldn’t have darks off to blue. I recon balancing the color was within their means and is likely their stylistic choice.
Looking at the results, it seems that the author defines a base color (green for the leaves) and moves up and down in brightness using what amounts to a multiplication for the shadows and an add for the lights. The result feels a bit harsh and unnatural.
I would suggest that he also plays a bit with the hue values.
1. That he darkens the lights but moves the green towards yellow.
2. That he lightens the darks, but moves the green towards blue.