A former student forwarded to me the following article concerning a visual way of understanding the Fundamental Theorem of Algebra, which dictates that every nonconstant polynomial has at least one complex root: http://www.cs.amherst.edu/~djv/FTAp.pdf. The paper uses a very clever idea, from the opening paragraphs:
[I]f we want to use pictures to display the behavior of polynomials defined on the complex numbers, we are immediately faced with a difficulty: the complex numbers are two-dimensional, so it appears that a graph of a complex-valued function on the complex numbers will require four dimensions. Our solution to this problem will be to use color to represent some dimensions. We begin by assigning a color to every number in the complex plane… so a complex number can be uniquely specified by giving its color.
We can now use this color scheme to draw a picture of a function
as follows: we simply color each point
in the complex plane with the color corresponding to the value of
. From such a picture, we can read off the value of
The article is engagingly written; I recommend it highly.
Mean Green Math 
Oh, that’s awfully good and I’d never thought to use color in that way to plot complex-valued functions. That’s a great notion.