What type of garter snake is this?

As I was watering plants today, I saw this garter snake laying on top of some ground cover in the sun with part of its body still under the ground cover. I estimate that it was probably between 30-36" in length. The body at its thickest point was about 1-1/4" in diameter. Typical garter snakes in my Zone 6 garden have brown or gold stripes and markings. This one had a brilliant turquoise blue belly. It was even more blue than the photo indicates. The snake didn't seem to mind me getting within 6 inches for a close-up of his markings. When I tried to identify this particular garter snake, the closest match was a "Florida Blue Eastern Garter Snake" (Thamnophis sirtalis sirtalis). I live in western Ohio, so I don't think I've identified it correctly. Can anyone guide me to a more logical ID?

I agree it looks like a garter snake, but an odd one.
Perhaps someone brought it home from vacation, then changed their mind and released it.

I've looked through hundreds of photos and descriptions of garter snakes, and none of them look exactly like this one. The closest is Thamnophis sirtalis similis, but even photos/descriptions of that one show discrepancies. And that snake is found in southeastern U.S. only, specifically Florida. So the odds are either that my snake was an Eastern or Common Garter snake with genetic anomalies or that someone DID bring this one back from Florida and it found its way to my garden.