彩虹感應卡是什麼原理

以下網址的魔術是什麼原理的?

魔術師展示六張不同顏色的卡片後，向觀眾說明：「自己將回過頭去，此時請觀眾任意選擇一張卡片，然後將這張卡片翻轉過來放，再和其它的五張卡片一起混亂後才通知自己回頭」。

魔術師回過身後收集全部的卡片，並依續的排列在桌面，最後魔術師卻在完全不知情的情況下，準確的命中觀眾所選擇的卡片。全部的道具亦可交給觀眾檢查。

The magician displays six different colored cards. He tells the spectator that when his back is turned he/she is to choose one card and then turn this card over and mix up all the cards. When all is done he/she is to tell the magician.
The magician collects all cards and deals the cards on the table one by one. Under this seemingly impossible condition the magician can divine the card that the spectator chose.

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