Further to the above, I’ve been playing around trying to find a way to get .active-page to work other than in Preview Mode, where it works perfectly.
I tried adding other features beyond just changing the text colour, and found they affected the entire site, like in the example below - trying to add an underline to the active page menu item underlines everything.
Is there some glitch happening @Norm which is also preventing my menu items from working properly i.e. turning blue?