Hi Charles,
Go to Customizing > Colors > Primary Navigation, check if the Background Current is set to black.
When we are looking at the home page, the Home button is the current button, so it uses the current background color which is black.
The Read button has a child menu item — Breaking news that shares the same URL with the Home button, so the Read button is treated as the parent of the Home button by the system, that’s why it shares the same current background color with Home button.
We can use CSS to override these rules though, let me know if you need further assistance 🙂