I do believe you're talking about florida blues. Thamnophis sirtalis similis. The more obvious blue striped dark background snake is a puget.

Similis isn't always blue, and to me, even the "blue" one's are more of a gray/blue. Often they are green or gray. Very blue one's are the exception really.

Gregmonsta's (not in the U.S.?) expecting florida blue:
http://www.thamnophis.com/forum/showthread.php?t=6521

Florida "blue"


Blue phase Puget:


Also a puget (not blue, red-spotted phase)



So, florida "blue" doesn't necessarily mean it's blue and just because it's a puget doesn't mean it's blue either.