From the Super Mario Wiki

Finleys form a group of dangerous fish enemies in Donkey Kong Country: Tropical Freeze. The Blue and Red Finleys look similar to each other and behave almost identically, continuously swimming on set paths; the only difference is their speed of locomotion, since Red Finleys swim faster than Blue Finleys. Green Finleys are entirely different from the other two variations, as they have a different appearance, are never faced in water and have different behaviors. All Finleys can be defeated with basic attacks.