Hi,

The kind of snake you're thinkin' of is the (controversial) ssp foxi: http://www.wildlifenorthamerica.com/Reptile/Blue-Racer/Coluber/constrictor-foxi.html

Otherwise, the Eastern yellow-bellied racer, C. c. flaviventris, is commonly referred to as the "blue racer" throughout its range, but its color never matches foxi's.

I had once the opportunity to see those at a French importer's and they were extremely attractive; a friend of mine bred them once or twice.

Hope that helps.

Benjamin