Nice analogy, I wouldn't have thought of that. But I'm unconvinced that this is a good measure of software complexity; for one, there are only three nontrivial complexity levels (2, 3, 4).
But it's also unstable: a circle with an odd number of nodes (e.g. a triangle) requires three colours, while a circle with an even number of nodes needs only two, even though both models seem similarly complex.
But it's also unstable: a circle with an odd number of nodes (e.g. a triangle) requires three colours, while a circle with an even number of nodes needs only two, even though both models seem similarly complex.