Please check the attached image and tell me how many Black legs you see.
Your first reply will probably be: just one. Nevertheless, according to the Catalogue, they are all Black.
Legs (as a minifigure part) consists of Legs (two limbs) and Hips. Unfortunately, Legs color is currently determined by the Hips, which are a smaller part of the assembly.
Suggestion: Change how Legs are catalogued – to reflect the color of limbs, not hips. If you agree, please upvote.
Comments
Some from BrickLink:
Hips and White Legs
Hips and Yellow Legs
Hips and Dark Gray Legs
etc