I'm no expert in this, and I'm not a food scientist, but it's my understanding that
- "Sushi grade" isnt regulated
- All fish meant to be served raw must be frozen at sub zero temperature for at least 48 hours to kill parasites
- The color of ahi tuna is indicative of which part of the tuna the meat is from; redder is considered more desireable because of its richer taste.
So your frozen supermarket ahi should be just fine! I've never seen a "not to be eaten raw or rare" warning. I've used the same from Albertson's for poke, with no incident. If you're worried about surface bacteria, a quick sear should put your fears to rest. But if you want that unctuous, creamy mouth feel you get from the ahi at Japanese restaurants, you'll have to pop for that $20 per lb stuff. Or catch your own!