CSS

on class hover another class color change

/* For wrapper is a child of item */
.item:hover .wrapper {
    color: #fff;
    background-color: #000;
}

/* For wrapper is another div and item is another */
.item:hover ~ .wrapper {
    color: #fff;
    background-color: #000;
}

modify another class on hover

A child element hover cannot effect a parent class or a class elsewhere in the code besides children and siblings. You'll have to use Javascript for that.