Col is the counterpart of Snort, except that in Snort adjacent regions must not be different colours.

The game was invented by Colin Vout, and was described and analysed in: Conway, John Horton. On Numbers and Games. New York: Academic Press, 1976. 91.

A fuller analysis was given in: Berlekamp, Elwyn R., John H. Conway, and Richard K. Guy. Winning Ways for your Mathematical Plays - Volume 1. New York: Academic Press, 1982. 39-41.