My apologies, I think I figured out my own problem while putting it together in codepen.
Essentially, I wanted a way, when a user :focus on an input, for the li outside of it to change its color, but that isn’t possible, since it’s on the outside.
Yep, you can’t link to other elements that aren’t related. What you could potentially do is use the sibling or adjacent selectors if the elements are one after the other.