Unwashed new jeans can lead to blue dye on your hands and shirt. When dye is transferred by friction, it’s called crocking, and the indigo dye in blue jeans is a notorious crocker. Before you leave blue everywhere, your washing machine is the first stop. Do a first wash with cold water, before the rinse cycle starts, stop the machine and add two cups white vinegar and let soak for a couple of hours. Then turn the machine back to finish. Hang and air dry your jeans, then press with the hottest iron setting.