Gender differences

Starting in Generation IV, Pokémon in the Video Games sometimes had minor visual differences depending on their gender, or gender differences. Some differences were easily visible, while some are hard to see without looking closely. An example is Magikarp, the male Magikarps have yellow 'whiskers' while females have white whiskers. When it evolves into Gyarados, the males 'whiskers' are the same color blue as it's body while the females are a lighter shade of blue.