23 colony expansions and only 2 expansions for the city. Don't count in those for diamonds. Diamonds are real money so who can afford them he has already a full city plan. BTW haven't used all mars colony expansions. Didn't need all of them to reach the goal and get colony function as it is supposed to.
Actually it is 4
1 new campaign, 2 new research expansions, 1 victory expansion