CrouchingBruin on "[Theme: Virtue] how to add active class"

how to add active class for navigational menu,
according to requirement when ever i click on menu button the active page menu as to become red background box

The active menu item will already have two classes, current-menu-item and current_page_item. You should be able to use either of those two classes to style the background on the active menu item, like this:

.sf-menu .current-menu-item { background: red;
}