V misreads my stack and makes a huge blunder, what would you do here?

All in and call.

Unless you are sure you were hiding your blacks, in which case you can let him off the hook for it. But why would you need to come here and ask? It’s entirely up to you. (Well, kinda. The floor might force him to call the full amount. Or force you down to the 300 max.)

The dealer said it's all-in and call. I'm asking what would do if you didn't purposely hide your chips but do not doubt V when he says he didn't see them. V is not asking for floor or demanding anything.

Do nothing. All in and call. You didn't do anything wrong, he made a mistake, and further isn't asking for anything.

Commiserate afterwards if you feel so inclined. "We've all misread a stack before" etc etc.

You had a total of 24 chips and villain couldn’t see two of them?

If you felt you did something specifically to hide them unintentionally, maybe you could offer a rebate or something.

But if they were in clear view, this is 100% on V and imo often times the fastest way to get people to break bad habits is to force them to face the consequences of their own actions. If you give them a rebate, they'll continue to pay little attention and next time this happens it'll be "Well LAST time the guy gave me a rebate, etc". It's not even like you pulled them out of your pocket silently. You gave money to the dealer who gave you the chips. Zero reason for a player not to notice that.

Tbf, this is a big reason why I have the unpopular opinion that black chips should never be on a 1/2 or 1/3 table. Even a 5k stack, which would be comically large, can be mostly colored up to green and it's a reasonable number of chips. Hell, I might even prefer some purple/yellow chips before black.

Results-- I didn't know if I was accidentally obscuring those chips after the hand started but I had no reason to believe V was lying. I agree with Ralwz I hate 100's at 1/2 for this reason.

I would up giving him a black chip rebate splitting the difference. I'm not a pro and it's not my income and ultimately $100 is worth it to me to have a clear conscience. If the V has any history of being a jerk or especially angle shooting I would have kept the entire pot without a second thought.

I guess the question I have is where the black chips were.

I usually keep my highest value chips in front of my other stacks. So I would have put the 2 black chips in front of my $5 chip stacks. In this case if there were also green $25 chips I would also keep them in front of the $5 chips stacks.

The other possibility is to put them on top of the $5 chip stacks.

If your black chips were in front of or on top of the red $5 chips I would not have given anything back. If they were under some red chips then it becomes a situation.

Since I have never been in this type of spot I really don't know what I would do but I think giving up $100 was generous.

The key issue is whether either you or the dealer properly announced you adding $200 before the hand started. It would be reasonable to ask for a floor ruling, and it is possible the floor rules the new $200 is not in play.

If left to the players to resolve themselves, really anything you want to do is fine. Full refund, partial refund, no refund. If you feel the $200 was clearly in play, you have no obligation give it back. But also if he says, look I was just trying to give you action as a a shortstack with a weak hand or air, and shows you his hand, giving it back is fine. But I would want to see his hand before deciding what to do.

I re-read the original post and I missed that the Black Chips were in front of your stack. In that case I wouldn't give anything back.

Your opponent clearly didn't see them but that isn't your fault. You did what you were supposed to do with the $100 chips. And as was mentioned above if you had lost the hand your opponent likely wouldn't have given your $200 back.

It would be interesting if your opponent had said "I would have given you back the $200 if I had won because I didn't know you had them and I would have made a much smaller bet" but I don't think he said that...

Whenever I am in your situation where the chips I am adding go over the limit (here the limit was $300) I always take the over chips off the table and put them in my pocket where the $100 bills came from. In reality you shouldn't have been allowed to have $310 on the table at the start of the hand and at the very least you should give $10 back.

A couple things... In your first post you kind of imply that you may have been inadvertently obscuring the black chips. That would pretty much be the only reason I would give him a rebate. Like if you were mindlessly shuffling chips and the blacks were in the pile you were shuffling, or the blacks were hidden behind your other chips or something. If they were in plain view you really don't owe him anything.

The other question I have is whether he said he didn't see how much you had before or after he saw your hand. I would be much less likely to give a rebate if he said he misread your stack after he saw your hand.

In general if you've been playing poker for a while we've probably all gone all in at some point thinking our opponent had less chips than they actually had. It's typically a "live with it" and "lesson learned" type of situation.