Unfortunately the whiskermenu doesn't integrate well with dark themes like Numix. Therefore I would like to request a dark theme for this nice plugin.
It's up to the themes to set the colors for Whisker Menu. I'm sorry, but I will not add theming to Whisker Menu itself. If your theme does not make it dark (for whatever reason), you can theme Whisker Menu manually: https://gottcode.wordpress.com/2017/10/21/theming-whisker-menu-redux/