The extra depth given by the darker brown is flattened by the green, because of the way you've just used it around the edges. The green (and brown) could be used to add wood grain texture, and the brown to AA between black and red.
I made an edit, not touching the branches ('cos I don't have time
) but just showing you a way in which you could add some depth.
I also found that the twigs are quite thick without the green/blue taking it away
In that last frame I just replaced the green with a default orange. I think it looks nicer