Meat

If it has been in the fridge, it should be fine.

I usually buy my beef in bulk, then separate into 1lb portions to freeze. My meat is almost always brown by the time I go to cook it, because it has been exposed to the air and light. (Same as my dad did when I was growing up.)

I have never, in over 20 years, gotten sick from it. We usually give it about a week in the fridge before tossing it out. You can tell if it goes bad when it gets a greenish tinge and smells wrong. (Which is easy enoug to tell if you can recognize the scent of good beef. Lol. )

The meat turns brown when exposed to light, it doesn't indicate that the meat is spoiled. I would go by the date on the package.

I go by the date on the package, and the smell.

I wouldn't use but my hubby would, and not tell me, and I would likely not even know.

It's all about the smell.

Undyed meat IS brown.
That said, I would not eat /cook meat that was sitting around, even refrigerated, for 4 days.

The brown outside is simply oxidation. The same blood that makes the meat look red starts to react with oxygen and turns brown.

The plastic wrapped packages for grocery store meat helps keep oxygen out and the meat stays pink. longer. Sometimes, CO2 gas is added which can prolong the pink look for quite some time. They do it because of how consumers react to meat turning brown. It's perfectly normal and safe, but people are often attracted to or repelled by colors.

Unless it has been improperly stored (left on the counter vs in the fridge) or is past the use by date or smells off when you open it, then the brown color is nothing to worry about.

I would go by the date on the package and the odor of the meat. If it still was pink on inside... I'd use it and just use it in a recipe where I need fully cooked ground beef.

I buy all my meat from a local butcher that's high end. That said... On my buying day, I wrap and freeze everything. I've had a time or two when I didn't freeze because I planned to use the meat. In those cases, I just fully cooked the meat and found a use for it.

Ground beef is not dyed.
Ground beef does not turn brown because of contact with oxygen. The meat turns red due to the wrapping being oxygen permeable. This is why you should re-wrap it before freezing. It's also the reason that vacuum packed meat (right after butchering) is typically more dark purple than red.

Exposure to store lighting as well as the continued contact of myoglobin and oxymyoglobin with oxygen leads to the formation of metmyoglobin. THAT is what changes the color from purple (with myoglobin at first before packaging) to red (with oxymyoglobin after exposure to oxygen), to brown (caused by exposure to both low temps and artificial light). Unless the meat smells bad, it's ok to eat after cooking. Even a "buttery smell" is acceptable. Throwing out meat purely based on color is wasteful.