The best I've seen is from the NPR article at http://www.npr.org/sections/itsallpolitics/2012/11/01/163632... .

One of these cartograms is a electoral vote cartogram of the US 2008 presidential election. Unlike the above examples, it uses a continuous color spectrum from red to blue (going through purple at 50/50) to represent the popular vote - which does a much better job of conveying voter proportions than the standard color every state red or blue. On the other hand, the map is geographically coarse grained on the state level - every state is shown in one averaged color. I have yet to find one that has both continuous color spectrum and is continous (ish) in space.