Style parent page and child page hopeless…

Hello peoples! I’m having a sort of a problem here… I have a menubar with 8 main pages. Three of those pages show a different colored menubar if the visitor clicks on it. I set the color of the parent page menubar in style.css with .page-id-23 #access {blabala}.
If I add submenu’s to any of the colored parent pages. The submenu shows up in the default color green. It does not show up in the color of the parent page. I would like to know how it would be possible to add a subpage in the admin panel (because it is for a cliënt) showing up with the same menubar color as the parent page.

I can also write extra css for the subpages(.page-id-23 #access {blabala}), but then I have to create the subpages first. I do not want that ofcourse. There is a way to create the subpages and having the same colored menubar as the parent page. But how….Can anyone help me out…..?