Each character has particular primary stat. Red is STR, green is DEX, and blue is QCK. STR is stronger than DEX, DEX is stronger than QCK, and QCK is stronger than STR. There are two additional types, PSY (yellow) and INT (purple) that cancel each other out. Send in a crew member that is stronger than the enemy's type to do more damage. If their type slot also matches their innate type, they will do even more damage.