The cards follow the lessons in each of the books. It is helpful to print the Beginning Level on yellow card stock because the Beginning Level Book is yellow. A separate deck is needed for each group. To keep the decks from getting mixed up, numbers - 1, 2, 3 can be written on the cards in each deck.
Level Once cards could be printed on blue card stock because the books are Blue.
Sample lessons from the books can be dowloaded from the Sample Section of this website.