Can't find to change bg color of menu on different screen size

Hello,

Consider use the Responsive Classes to add Different Background Colors for Headers on different devices. Example:
[ch_pre type="css"].device-lg #header-wrap {
background-color: #FFF;
}[/ch_pre]

The Responsive Classes are as follows:

.device-xl – Class for Large Devices >=1200px

.device-lg – Class for Medium Devices >=992px to 1199px

.device-md – Class for Tablets

.device-sm – Class for Landscape Mobiles or Phablets.

.device-xs – Class for Portrait Mobiles

You can add these Custom CSS codes in the css/custom.css File.

This will definitely work fine. Hope this Helps!

Let us know if we can help you with anything else or if you find any further issues.