A Collatz Conjecture's Bonsai

I've recently made this, after seeing xkcd’s cartoon about the ^wpCollatz Conjecture. May be just me, but I rather like it. It was made iterating from 1 to 10000, and calculating the possible paths of each number. If it leads only to its double, then it's blue; if it leads also to an odd number, red; the grey ones didn't get iterated, but were calculated implicitly by doubling the previous ones. Et voilà!