Background Color Change, Inserting banner img & Header Font/Button Size Change

I need to be able to change the background color in the areas with the red outlines

Why is the header background color (the green area) slightly different than what is chosen, even if the tint is set to off?

I need the menu items in the purple area to be Forums, Groups, Shop, Blog, Contact, Constitution, “Guild Applications”. If I make the last item the correct words it makes the header double height. I need to make the words in it smaller or larger based on the menu bars contents, or at least be able to make the font/buttons smaller.

I also need to be able to place a banner where the green area is, when i try to place the owl slider into my homepage i get an error message when the homepage is opened.