Legwear

Shorts are a type of unlisted attire in Splatoon, and proper clothing items in Splatoon 2 worn by Inklings.

Splatoon
In Splatoon they are not changeable and always have the same appearance: black, with a stripe of the wearer's ink color on either side. They have no other role in the game whatsoever. The only gear that does not have the standard shorts are:

Splatoon 2
In Splatoon 2 pants are avaliable as default customization options much like hairstyle, eye color, and skin color. Shorts can be changed into different types, including skirts with shorts and capris for girls as well as loose shorts with leggings and looser capris for boys on top of their normal Splatoon shorts. As of the 2.0.0 content update, female Inklings now have a choice to wear a longer, skintight version of their original Splatoon shorts as well as looser shorts, while males now have a choice of skintight pants down to the ankles and long, loose shorts.