That's really a nice tree starting. Maybe I'd just make the top a little lower (see the ghost ellipse at the top).
As for the colors, The one with "same tint as the grass" would imho work very well as level borders, non-interactive, tree. The other one (original colors) stands out more, so I'd use it if I'd want the player to notice the tree as one having some special feature. The shall-I-use-my-pegasus-boots tree.
Is the "pacman mouth" effect on the right (on the original-colors-tree) intentional ?