That grayish-brown tuna is safe.

Yes, it’s safe. That discoloration is just oxidation or a little bruising — not spoilage.

Fresh tuna gets its deep red color from myoglobin, the same protein that makes beef red. When exposed to air, that myoglobin oxidizes and turns brownish-gray. It’s the same reason a cut apple turns brown. The tuna was probably cut a few hours earlier, or the piece was resting against something in the package.

Smell it. If it doesn’t smell sour, ammonia-like, or “off,” and the texture is still firm and moist, you’re fine. If it smells like low tide or feels slimy, toss it. Color alone isn’t a reliable freshness test for tuna.

Trust your nose, not your eyes.