Views sorting with list item text
The best way to accomplish this is to use a term reference field rather than a list field, for a number of reasons:


The taxonomy module is made specifically for categorizing things, so it's a natural fit for  a "Category" field.
You don't have to edit your Category field every time you want to add options; you can simply add more taxonomy terms. This is better for Features-driven development (assuming you've exported your fields to code).
You can sort by the taxonomy terms' titles in Views by using a Views relationship between the node and the term via the term reference field.


AFAIK, there is no way to sort by value labels in a list field like you're trying to do. I'd definitely recommend going with a term reference field instead.