How do I change the indoor footwear?

I have the option set to wear slippers indoors, and they automatically put some on, but I read that I had the option to change them. I wanted to change them to a different pair of slippers or at the very least, change the colour of them. Whenever I open CAS there’s no option to change indoor footwear and if they are wearing the slippers when I go to Cas, they disappear and their normal footwear is on so I can’t even change the colour. How do I do this?