I always have a deck on me, most of the time several. Since I dont have a lot of decks I cant really match them to my outfit (wich is also mostly black) but I wouldnt care even if I had a fitting one.
I use a plastic deck when I´m outside, waterproof, washable, durable. Perfect for cardistry in the rain or letting cards fall down into the mud ;P But most of the time I have a paper deck on me as well for fans and such.
No matter where I am, doctor, bus, shopping line, I practice. Its just to much fun.
