.classname.newClass:before {
    background-color: yellow;
}

$(".footer_block span").on("click", function () {
    $(this).toggleClass('active');
});

.footer_block span {
    background: url("../img/footer__bg-1.png");
}
.footer_block span.active {
    background: url("../img/footer__bg-2.png");
}