Player Settings
From Inkipedia, the Splatoon wiki
Upon starting the game, the player is given a variety of options to customize their inkling or octoling.
Splatoon
After deciding on the gender of their inkling, the player has the option to change the following.
Skin tone
Eye color
Splatoon 2
Splatoon 2 added the ability to change the player character's hairstyle and leg wear. The Octo Expansion update added the ability to play as an octoling, after beating the campaign.