# Different Coloring of Julia Sets

I have known about Julia Sets for a while now, and today I had an idea about the coloring of Julia and Mandelbrot Sets. What if someone were to color them not only by how quickly z diverges, but also how quickly it converges. How would I go about doing this in a program? Has it already been done?

Furthermore, this is really the only way to go when drawing Julia sets for rational functions. Here's the Julia set of $z^{-2}-1$: