Trouble with Mobile navigation appearance

My desktop website theme is set for buttons to have a WHITE text over black buttons.

When accessing my mobile site, the navigation drop-down menu is blank because those same page links are WHITE in color as set by the desktop settings.

How do i change the button link color for my mobile site so it doesn’t affect the button links on my desktop site?

I’ve looked everywhere on my WP theme settings for a separate theme settings for the mobile site and can’t find any.

Thanks for any help.