The basics of Colorado are that it is played with 2 decks of cards and comes from a family of card games that include: Sir Tommy, Calculation Solitaire, Sly Fox, and Strategy.
Colorado takes an interesting turn from the usual card games by having two sets of foundation piles with slightly different rules for each.
In this version there are 8 founation piles. 4 on the left and 4 on the right. Both sets of foundation piles are built by suit (as you’d probably expect). The four on the left are built from Ace ascending (probably also how you’d expect), but the four on the right are built down from King to Ace.
You win the game by getting every card to the foundation piles.
Whenever you move a card from one of the tableau piles to a foundation, if the space is now empty, you must immediately fill the empty space with a card from the stock (if you are playing this version online, the game will do this for you automatically).