Double is a cute color domino.
The game has 72 cards. Each card is subdivided in 3 colored sectors with a card value from 1 to 7.
The player has to get rid of his cards as fast as possible by putting them to the both ends of the open card line: yellow part aside yellow, red aside red, a.s.o.
The Player who gets rid of his cards first is the winner.

It appears that this game is very similar to, but not the same as On The Double, also by Maureen Hiron.