Python implementation of an experimental Four Color Theorem algorithm based on Tait edge-coloring, graph reduction, and Kempe-chain color switching.
The homepage with the full story is 4coloring.wordpress.com.
This graph was colored by the Python program:
It has 1,996 vertices and 2,994 edges. Starting from its planar representation, the historical run took about ten seconds. See the algorithm write-up and download the DOT input.
Videos of the Python and Java programs are available on the project YouTube channel.