looks like you need to sand more, till you get to the lighter/white area.

Sanding is about the worst way to remove paint available.

What that looks like is you have sanded through the veneer in spots and are down to the core wood---if you are lucky, that wood is soft maple. Usually it is a junk wood like poplar or pine.

By junk wood, I mean it us meant to be covered and never seen.

The gotcha if the wood is maple is maple is very difficult to color evenly without pretreatment and a bit of experience. The fuzzies are usual with poplar and to some extent with soft maple after rough sanding processes.

The second gotcha is the top is most likely not flat---the usual result of using a belt sander and will show dips/etc. when finished.

Not much you can do now except sand the rest of the top to match and try staining or dying---which will undoubtedly blotch and look terrible(because of the wood).

Or, prime and paint.

Thanks kindly for all of your thoughtful feedback. What if I cut a thin piece of unfinished wood to size and place it over the table top? I could then glue the pieces together.and then stain it. Hopefully that'll make it look seamless.

Thanks!

Next time, pick yourself up some Citristrip. If you leave it on overnight and don't fuss with it, it'll even suck the stain out of the wood.

How would you finish the edges of this unfinished wood? I think, if you go this route, you're better off to get a matching veneer.

I don't mean to be unkind, but one can't argue with the truth. Unfortunately, you really messed that table up. Belt sanders have no place in refinishing furniture. I was lucky. Someone stopped me before I did the same.