1. Transparent menu:

2. Transparent menu option has no influence on top bar color (look at example below):

3. When you use the transparent menu option, the submenus will have a little bit darker background than standard submenus

Setting transparent menu:

1. Edit a page

2. Change the page header for "transparent" 

3. If you prefer, you can choose a "Transparent - dark gradient" option instead of the "transparent" option. It ads a dark gradient background (picture below) to the menu so it's white fonts are more visible

4. Click the "Update" button