Hi,
Thank you for your patience, and I apologize for the inconvenience.
I have checked your website and identified the cause of the issue. The section background color is not explicitly set in SP Page Builder, so it inherits the body background color defined by your template.
For some reason, when the off-canvas menu is opened, the template changes the body background color, which causes the section background to change as well.
Since the template you are using is not one of our products, we're unable to provide a solution for the template-related behavior.
As a workaround, you can set the section background color directly in the SP Page Builder section settings instead of relying on the template's body background color. This will ensure the section retains the correct background color regardless of any changes made by the template when the off-canvas menu is active.
Please let us know if you have any questions or need further assistance.