Not sure if this is done right. Could I speed it up by using Set instead of SetDelayed in the converter to complex point? If so, shouldn't I protect the "z" by wrapping the definition in a Module with "z" as a local variable?
I have the coloring going from green for 0 to red for Ï and then back again, so colors are the same for plus and minus arguments (i.e., angles) for the complex polynomial. Probably should have some indication which is which, or a way to toggle it.