They both can have blue or green heads. I copied this for you.
Very similar in appearance to T. o. ornata . A main difference is the number of radiating lines on the second pleural scute. Luteola has 11 to 14 radiating lines on the 2nd pleural (Ernst and Barbour, 1989; Legler, 1960; Smith and Brodie, 1982) that are lighter in color than Ornata which has 5-9 radiating lines.
If you post some pictures we can tell you what you have.
I agree with Kimber. It's mainly the number of radiating lines and the deserts usually lose coloration with age whereas the ornates usually retain a more distinct pattern. I've heard from people who keep both subspecies and supposedly deserts and hardier turtles and easier to keep
Yes thats another way to tell as well the radiating lines, I had 60 of these guys at one point and i swear these guys are super hardy. I'd take in those that were ran over and i'd repair their shells and they'd recover with no problem...very opportunistic. My dogs never messed with them, a few bites on the nose was all the wanted....they'd get so mad when one of them would crawl into their water bowl.
Here's a pick of one of my ornata ornata, i'm trying to find some pics of my deserts.