Wow! A gimmicked deck that is easy to use, packs a double punch, and is affordable. This is the trick no-brainer trick that I use if I mess up, or need something of substance.
The effect is simple. The spectator thinks of a card. You fan through a deck and their card is face up. You ask them to pull their card out. Lo and behold, their card is of a different color that the rest of the deck.
Other than a tad bit of counting and memorization, that is all that there is to performing this trick. The effect is mind boggling, and can technically be performed right afterwards, but, none the less, it is better left alone. My reactions are always great to this one. The Brainwave Deck is definitely in my top ten.
My only few minor things about this are that the deck won't even seem real to the spectator. They will suspect a trick deck. While confrontation can be avoided with a witty response. Also, sometimes pulling a blue deck out of a red package is a little odd. Nobody has ever said anything to me, but it is still a little fishy. Finally, while this one will come with practice, and depend on how often you handle the deck, sometimes a different card will be revealed face up prematurely, and by accident. While, as all mistakes, this can be covered up, it is still a little nerve-wracking. Those comlaints are an example of me being very critical. While it ended up that I talked more about the bad things than the good, the good is so good that it overpowers my minor quibbles.
You'll also need to word this trick up a little. As is, the trick is short. However, you could take my ideas or add some of your own, to stretch it out and make it more mystifying.
Also, for those of you who might go with the invisible deck because it seems less likely to seem like a trick deck, I'd still advise you stick with the Brainwave. Its illusion is more extravagent, and, if need be, you don't have to show the backward card's different color. Also, if you want to be creative, you could turn this into a trick where you claim that you will "change the color of this indifferent card". You could come up with different "dissappearing card to a different deck" routines as well.
In the end, this is a must-have for mentalists and card workers.