IE8's menus don't all have normal styling. In particular, the submenu 'arrow' turns white when hovered (rather than staying black), and disabled items have a different text colour and selection colour when hovered (compared to normal menus). See the screenshot for a comparison. This only seems to apply for menus accessed from the 'Command Bar' (menus accessed from the legacy Menu Bar are normal, with the exception of the Favourites menu which is fake).
Use native menu styling.