menu colour change

You could try these css

For background color

#nav-main .current-menu-item {background-color: #FFF;}

For text color

#nav-main .current-menu-item a {color: #000;}

If these don’t work, add !important at the end of the values.

Thanks – can you tell me where to add these please?

Frontier Options -> Custom CSS

Brilliant! Thanks so much for all your help

Just marking this as resolved.