As you style the website to match your branding colors, you may wish to change the main menu underline hover color on desktop views.
To do this:
1. In your WP Dashboard, navigate to Appearance > Theme Editor > style.css > Line 145. You'll notice that the line reads: background: #15bf86; /*** COLOR FOR UNDERLINE ***/;
2. Change the hex code to your desired color value.
3. Save your settings by clicking the "Update File" button, and Shift+Refresh the front-end to review your new main menu underline hover color.