Cognomen Колби (Colby 
, Colbie 
, Coulby 
) , in all the world, is a common surname. The surname Колби is characteristic of the United States, where it is quite a rare surname, Canada, and New Zealand. Not in comparison with a country's population, it is the most numerous in the United States, the United Kingdom, and Canada. Likewise, Колби is the forename as well as the last name.