Player cards are colored based on how rare the players are.

The more rare a player is the more potential the player is born with. So a highly rare player 1) has better starting attributes and 2) will develop more when trained than a common player and end up being a much better player later in his career.

The 7 rarities are:

- Common (grey card - worst)

- Uncommon (green card)

- Rare (bronze card)

- Super rare (silver card)

- Epic (gold card)

- Legendary (special red card)

- Mythical (special purple card - best)

TIP! 

An epic/gold card player at age 25 who has been trained poorly during his career can be worse than a rare/bronze card player who has been trained well. Rarity is given to a player when he is 17 years old and sticks to him for his full career. 

So if you are buying an older player, scout him first by looking at his quality, skills and developement maximum. Don't be blind and buy older players just because they have a nice card color. Rarity matters everything for youth players but less and less the older a player gets where quality starts to be the most important metric to look at.