Cool! A lot of work involved in that stick.
First off, the scales are remarkable.
I've seen a few snakes in the wild, and certainly enough in pictures, but I've never paid much attention to the specifics of the patters. So I don't know what direction your painting may take.
I can comment on paint colors. Painted some myself, and have a number of friends who are pretty accomplished.
One trick that a number of them used was to first paint a contrasting color to the final surface color that would go over it over it. For example, a bright red that would eventually be covered by green leaves. Where the top layer(s) of pigment were opaque, the final color would be evident, but where it would be thinner it would be somewhat browned out from showing the underpainting, making for subtler color. Intentionally, the area would not be completely covered, allowing the contrasting color to "pop" the edges of the area. A more subtle way of outlining spaces w/o resorting to just a dark line.
One problem w. using contrasting color is that they can cancel each other out. It can be tricky to get the right balance of area so the eye doesn't mix the two into a grey somewhere in between the two. Personally, I've used a method that uses 3 tones with good results. There is a primary color. Then there is a related companion color, used in small quantity, that is similar to the base. In the case of the light yellow green snake, perhaps a bit of darker green that is a little bluer. Then the contrast color might be either shifted from red toward magenta, keeping the contrast from negating the prime color, and becoming somewhat resonant w. the companion color.
But I don't know if this method in any way would suggest a real snake, or just a phantasm.