[baggins]

if he doesn't know, then he could just as easily have shown you a black card. showing you a red card means that now you both know that there is one red and one black left, but neither knows where. whats the point in switching then?

if he knows, however, then of course he's going to show you the red one. every time. and then give you the option to take the worst of it, instead of giving you even money.