Hi Reksamwestend,
Thank you for feedback.
To change color, background, font-size... change anything, You need to use the development tool of your browser and move the mouse to the point of change, right click select inspect element. Then you'll see the content of section you choose and the CSS. Find and edit the attributes affects the style as you want.
After to edit, you need to remember the location and editing the properties to add to the menu CSS file. This depends on your site, class. Some case it can be overridden by CSS template it make your menu style not working. You should be add important attribute for element.
MegaMenu color change
