Trouble with Child Theme Menu Bar

Are you guys able to change the colours of the child theme you’re using and still retain the shape and functionality of the menu bar?

I am using the Rocky Red child theme and if I don’t use the default colours, the menu bar goes wacky. Loses its form and basically doesn’t look or act like the demo.

Wondering if this is normal or not as I’ve tried investigating this issue for a while with no resolution.