<!DOCTYPE html>
<style>
option {
    /* background-color and color are overridden for checked options */
    background-color: lightgreen;
    color: red;
    /* properties other than background-color and color apply to checked options */
    padding-left: 20px;
}
option:checked {
    /* properties other than background-color and color apply normally */
    text-decoration: underline;
}
</style>
<select multiple autofocus>
    <option>foo</option>
    <option selected>bar</option>
</select>