Change background color for header/nav on single post

Hi there,

Try this CSS:

body.single .main-navigation, body.single .main-navigation ul ul {
    background-color: #000000;
}

Adding CSS: https://docs.generatepress.com/article/adding-css/

Let me know :)

Perfect, thank you!

One more thing. How do I change the text color in the slide-out menu in single post?

Looks like I figured it out myself. Thank you.

Glad to hear :)