How about presenting a miracle where a thought-of card, signed and removed from a normal deck, changes color? 
And, the deck had already been examined and shuffled by the spectator!!! 
Without any change? 
This is 
BRAIN WAVED: 
A new method for a miraculous effect! 
When a normal card, freely chosen (or simply thought of prior to its being removed from the deck) changes color... 
Keep in mind that everything is done under these strict conditions: 
- You are using a normal deck (examinable before, during and after the trick) 
- It is shuffled 
- A card is chosen freely (or simply thought of prior to its removal) 
- This card is taken out of the deck and signed 
- The spectator can change his mind 
- No force 
- No accomplice 
- No change 
At the end of the effect, you can leave the card as a souvenir with your phone number, for example. 
In the spectator's mind, there is nothing. 
Nothing, nothing and nothing. 
Everything is clean. 
This is maybe the most magical: get such a result with all these conditions!