Child pages don't keep parent page in menu highlighted

I've found a few posts that sort of address this problem but haven't found anything that solves it:

When I am on a child page, I would like the parent page name in the menu bar to stay its rollover color.
For example, the parent page is called "Buy Stuff"



When I'm on the "Buy Stuff" page, the words "Buy Stuff" in the menu bar are red, to differentiate it from pages that I'm NOT on.

But when I click on the child page, called "Apparel", the "Buy Stuff" turns back to black, so no one knows what parent page "Apparel" is related to.



I would like for the parent page to stay red in the menu bar when I'm on the child page.

Any ideas?

Thanks -

ALSO: the same goes for the child pages. I would like for the sidebar menu item to stay highlighted when I'm on the actual page I've clicked on.