The Divi theme appears to have a glitch that sometimes happens, where the theme color and the header will change mysteriously. It seems that this usually happens when someone is changing or modifying the menu or header.
Furthermore, it seems that this can be prevented, possibly, by changing a setting, as follows:
We need to disable “Static CSS File Generation by going to: Divi > Theme Options > Builder > Advanced > Static CSS File Generation > Disabled
If this does the header or color scheme randomly changes again, after this setting has been disabled, please note the circumstances surrounding this event in as much detail as possible.
This solution was originally found in the following Divi forum thread:
https://divi.help/threads/header-changes-colour-randomly.1914/