It seems to me that many mysteries involve hats. Therefore, a good old hat mystery that I came across a couple of years ago.
Abraham (A), Bingchiang (B), Charly (C) and Derek (D) are sitting in a line facing the same direction in that way that A can see B, C and D. B can see C and D, C can see D and D can see no one.
> > > > A B C D
Ernest is a rich guy that has 5 hats. He shows them 3 white hats and 2 black hats that only differ in color. Thus, they feel exactly the same way. Of those 5 hats, he randomly picks 4 hats and puts one hat on each person's head. The remaining hat is destroyed.
Ernest claims that if one can guess which color his hat is, they all will receive exactly 625000 dollar.
Ernest says that A has to go first in guessing, then B, then C and then D. If one of them miss guesses his color, all would die instantly. However, if they don't know their color, they just can say that and the next person would be able to guess.
Abraham answers first: I can't guess the color of my hat.
Bingchiang doesn't speak English so mumbles something weird which no-one could understand. Ernest decides that it doesn't count as a wrong answer but that he just lost his turn to guess.
Charly also answers that he can't guess the color of his hat.
Derek is a smart man and knows the color of his hat. He gives the answer to Ernest and they claim their prize rightfully.
Do you know what Derek's answer was? How did he know what color his hat was? Do you know even more hat colors (Abraham's? Bing's? Charly's?)?
PS: no-one is a chameleon or some sort. Every name is linked to a normal human being without super powers.
SPOILER ALERT: A lot of the answers below are not provided with the spoiler alert tag. Beware if you scroll down!