Chane bg colour in menu bar?

You have to add custom CSS. There are plugins for this you you could use Child Theme.
Here is an example code:

.menu {
    background: green;
}

and of course you could replace the ‘green’ with your desired color hex code.

Keep in mind that most likely you will have to change the sub-menu background and selected menu item background.

do you have the code for using the colour on the bottom banner as well?

What do mean by “bottom banner”? If you are talking about Footer section with copyright text you could use this:

#footer {
background: green;
}

Thnx. Youre great!