Use different menu colours on Dispatch mobile and desktop menus

Hello, asking for advice on the Dispatch menu please...

The original colour for the sticky menu header on the site we are creating was black (on white background), which worked well because the secondary menu is on a black coloured border.

However, on the off canvas mobile menu, the black on white format has much less visual impact.

So we used a reddish-brown colour for the off canvas mobile menu (which looks better); however this change also affected the desktop header menu colour and diminished the visual impact of the matching black menus.

Is it possible to have the best of both worlds, i.e. keep the black & white scheme for the desktop header menu, and a different colour scheme for the mobile slide out menu?

Many thanks,
Brenda