[Theme Horse Support Team]

Hi Sebastian,
Are you trying to put border in the featured image of recent work here in our demo ?
https://www.themehorse.com/preview/interface-pro/

For top line of the drop-down menu color. Go to Appearance -> Theme Options -> Design Options Tab -> Custom CSS paste the following CSS code and Click on save all changes button:

#access ul li ul {
  border-color:#4A89C3; // change this hex color
}

Thank you!