1.) Get a ddeck of cards
2.) Keep only the Number cards 2-10
3.) Shuffle
4.) Sort the new deck into decks of Black and red
Iv done it and i only had 2 misses. I know its a 50/50 chance but thats not what this is about. Almost everyone knows what red and black looks
like. So when you do this try to get a feel on the card whether its black or red. It should only take 1-3 sec per card to know its color.
If you want you can look at the card after your guess(Try to know not guess) or make 2 piles face down and analyze them after your done.
I've done this before and had them all come out perfectly. Unfortunately I was using a marked deck and it was a magic trick . But in all
seriousness, it sounds like good practice though.
I find it is better practice to use shapes like squares, circle, line. star etc. it allows for more visualization and mental stamina as opposed to
just colours.