Use :hover to modify the css of another class?

There are two approaches you can take, to have a hovered element affect (E) another element (F):

1. F is a child-element of E, or
2. F is a later-sibling (or sibling’s descendant) element of E (in that E appears in the mark-up/DOM before F):

To illustrate the first of these options (F as a descendant/child of E):

.item:hover .wrapper {
    color: #fff;
    background-color: #000;
}​

To demonstrate the second option, F being a sibling element of E:

.item:hover ~ .wrapper {
    color: #fff;
    background-color: #000;
}​

In this example, if .wrapper was an immediate sibling of .item (with no other elements between the two) you could also use .item:hover + .wrapper.

JS Fiddle demonstration.

References:

• CSS 2.1 selectors, at the W3.org.