Generic mana cost
A generic mana cost is represented by a number or an X in a gray circle (, , , , , and so on).
Rules[edit | edit source]
Difference with colorless[edit | edit source]
There is no such thing as "generic mana".  Though you can use colorless mana to pay for generic mana costs, they are not the same thing. "Generic" is a type of cost. "Colorless" is a type of mana. You can't produce generic mana, but you can produce colorless mana and have a colorless cost (first introduced with Oath of the Gatewatch).
R&D came to the conclusion that they had to stop using the mana circle with a number to represent both generic and colorless mana. Changing the representation of colorless mana was easier, as it's represented far less, so they to made the new mana symbol . This change was made along with the rules update for the expansion Oath of the Gatewatch, which features colorless as well as generic mana costs.