Diabolical Envelope

The magician has an envelope, inside there is a card with its blue back, its prediction.
Then he takes a bunch from the red back and a spectator chooses a card, absolutely without any forcing!
The wizard invites the spectator to sign the face of the card.
The viewer returns the card, so the magician inserts it into the deck, which cuts and blends.
 
Now the bunch is on the table, the wizard shows all the sides of the envelope and says, "The preview card to be correct should have the same color as the chosen backdrop."
So the magician turns the color of the paper inside the envelope and says, "Now it looks just like the paper you choose." Immediately shows that all deck cards were different!
 
The Wizard opens the envelope to extract the preview card and shows the inside, which is completely empty!
The Magician gives the card to the spectator and says, "This is not just a prediction ... it's your card!"
 
IMPORTANT POINTS:
1. NO FORZATURE - The spectator chooses any card.
2. NO DISPENSES - No paper to be worn.
3. NO ADHESIVE TAPE - No adhesive or double-sided tape outside the envelope or cards.
4. SIGNATURE ON THE PAPER - The spectator really signs the chosen card, not a duplicate.
5. CONTROLLED TRANSFORMATION - The magician freely chooses the moment of transformation.
6. ALL DIFFERENT CARDS - All cards in the deck are different.
7. EMPTY BUSY - The magician shows the empty envelope, and his face / eyes are visible through the transparent window.
 
IS PROVIDED:
- The Diabolical Envelope gimmick.
- Full video explanation of the routine.