The brown spots are usually dead, but can sometimes surprise you by resprouting from their roots. Yellow, red, and whatnot are generally just shocked.

Spreading grasses will fill the holes if your grass spreads.

Realizing the vagrancies of cats, it can be hard to water the spots where they pee. If possible, though, diluting the places the cat goes will fix the problem if you get there fast enough.

Try this: scatter a heaping handful of table sugar on the spots and report back in 3 weeks. My grass returned and grew much faster than the surrounding grass right in those spots treated with sugar.

Will do. Can't hurt to try. I bet my pet rabbit will eat all the sugar though lol. She's a mega sugar addict.

Do you suggest sprinkling the sugar on dry, damp or flat out wet grass?

Dry, but you can then water it in a little to keep your rabbit from going after it.

The sugar causes a bacterial explosion that also requires a lot of nitrogen--which they'll get from the pee. That gives the grass plenty of now neutralized soil to recover.

The bacteria will die, but slowly enough that there won't be a massive release of nitrogen.

Extremely well said, morph. I could have said the same thing except I would have compacted it into about 1,000 words.

Will do. Can't hurt to try. I bet my pet rabbit will eat all the sugar though lol. She's a mega sugar addict.

Do you suggest sprinkling the sugar on dry, damp or flat out wet grass?

Dry grass by preference, but damp or wet won't cause any issues.