\Show a glassy die and 4 cards, each card in a different color. Ask an audience volunteer to freely choose one of the colored cards. Then place the selected card in the glassy die and cover it. Do some magical moves and uncover the die -- WOW!! The die's color has changed to the selected color!
This effect is both MENTAL AND MAGICAL - the die "knew" the selected color (mental) and changes into that color (magical)! It can be performed in any place to enthrall all audiences!