Change background color for dropdown hamburger menu

I can’t find a setting in Appearance >> Customize >> Colors to adjust the background of the dropdown hamburger menu. What should I do?

site is https://chromawords.com

Hello, please check this topic:

Please feel free to ask any other questions that you might have.

Kind Regards, Roman.

Thank you! I added this code and selected my colors. However, I now see a black border around the background box. How can I change the color of the border?

Hello, please try to add this CSS code as well:

#masthead #mainnav-mobi ul li {
    border: none;
}

Kind Regards, Roman.