Does ground beef turn brown after freezing?

I bought some beef back in January. I froze it in 1.5lb packages. We took it out to thaw Tuesday morning. It's now technically Friday morning and I took it out to cook it for sloppy joes. When I unwrapped it, it's almost completely brown except in the middle where it's still red. Unfortunately I can't smell because I have a cold. I would think if it was spoiled it would smell horrible and I would be able to smell it at least a little. Is it going bad? Or does ground beef normally turn brown when you freeze it?