This can be done using an attribute selector.
[class~='list']:last-of-type {
background: #000;
}
The class~
selects a specific whole word. This allows your list item to have multiple classes if need be, in various order. It'll still find the exact class "list" and apply the style to the last one.
See a working example here: http://codepen.io/chasebank/pen/ZYyeab
Read more on attribute selectors:
http://css-tricks.com/attribute-selectors/
http://www.w3schools.com/css/css_attribute_selectors.asp