menu color

You need to also target the submenus in your custom CSS:

.main-navigation ul ul {
  background-color: #bb00bb;
  color: #fff;
}

Replace the example purple with your own colour.

If you need further help, could you provide a link to your site or paste your relevant custom CSS here, between code tags?

Hello Kathryn – How do you also change the text color in the submenu?

The attribute color refers to the text colour, so if you change the code from white (#fff) to something else, that should modify the text colour in the submenu accordingly.