Active Text Link Colour

Please can you advise me on the css to show the active text link in a different colour? I am using the boxed layout, logo above menu.

None of the solutions I have found work.

Here is my latest text:

.header_color .main_menu ul:first-child > li.current-menu-item > a, .header_color .main_menu ul:first-child > li.current_page_item > a .avia-menu-subtext{
color: #555555 !important
}

I also have these applied:

#top #header .av-main-nav > li > a:hover .avia-menu-text, #top #header .av-main-nav > li > a:hover .avia-menu-subtext, .html_bottom_nav_header.html_logo_center #top #menu-item-search>a:hover {
color: #5CB0E5;
}
#top #header .av-main-nav > li > a .avia-menu-text, #top #header .av-main-nav > li > a .avia-menu-subtext {
color: #2c82b8;
}

Many thanks in advance.