The ball problem

Mr. Singsong distributed out 4 bags to Allan, Brian, Charlie and David. He said: Each of you have a bag of red and/or white balls. Every bag has 3 balls. The numbers of red balls in all bags are different. Even each bag has a label to indicate what each bag contains, all labels are completely wrong. Now, you can take out 2 balls out from the bag and then tell me what is the color of the third ball.

Allan took out 2 red balls from his bag. After he compared the label he told Mr. Singsong what the color of the third ball was immediately.

Brian took out 1 red ball and 1 white ball from his bag. After he compared the label he told Mr. Singsong what the color of the third ball was immediately also.

Charlie took out 2 white balls from his bag. After he compared the label, he could not tell what color of the third ball was.

However, David said to Mr. Singsong: I can tell what color of all my 3 balls are. He did it correctly. But how?

Also, can you tell what label said and what kind of balls each person had