I'm not exactly sure how you are getting the context (or flyout) menu color in your screenshot. The default for this menu is a translucent black.
To change the Context (Flyout) menu color:
Open RegEdit (Win+R and then type regedit and hit enter).
Navigate to HKEY_CURRENT_USER\SOFTWARE\Stardock\Start8\Start8.ini\Start8
Right Click the Start8 Key and select New>String Value
Name it: S11_MenuStyle
Now right click this new string and select Modify
In the resulting dialog enter 2 for the Value Data
Close RegEdit and then Restart Explorer for the change to take effect.
The Value Data has 3 options:
0 = translucent menus;
1 = solid menus;
2 = color tinted translucent menus
You can select the highlight color for this menu in Start11 as follows:
Now open The Windows settings and navigate to Personalization>Colors and scroll down to "Show accent color on Start and Taskbar" and turn it on, and then select the color you want to make the background of the Context (Flyout) menu.
NOTE: This wont affect the Start menu or the taskbar choices you made in start11. It will change the color of the Windows Notification menu, the highlight color for buttons in settings, and the bar underneath the app in focus on the taskbar.
Example: Seafoam color chosen in System Settings and blue chosen in Start11 "Selected item accent color."
Good luck! Let me know if you have any questions.
