How many feets?

I know that humans are weird and put feets over their feets, but I saw something strange today.

I has four feets.
They're fluffy and they're all the same colour - black.

But I suddenly saw that my human and the female human has lots of different feets to put over their feets.

They has red feets, and brown feets, and pink feets, and white feets, and black feets, and stripey feets.

Why would they do this?
What's wrong with one set of feets, in one colour?

I like my feets.