I have a bit of an odd issue going on.
1) On my main forum page the navigation widget menu displays ok is, apart from the background color orange being the same color as my text and trying to find how or where to change the color setting for this one item is proving difficult, as I see nothing in the documentation.
2) Worse still, when I visit my profile page I see a full orange block where the menu should be.
I don't understand why the Navigation menu widget would show differently from one page to another?
The wrappers are different, so the tree of CSS classes are different too, they can't be identical. The wpForo sidebar is an extra sidebar loaded in page content, it's not the a regular sidebar of your theme. If you want look them identical you should use the right sidebar of your theme instead of wpForo sidebar. Just remove all widgets from wpForo sidebar, then change forum page template from full width to 2 col with right sidebar.