When the SideMenu is presented, the status bar background color automatically turns black.
I haven't set any status bar background color for my app, still when the side menu is presented, the status bar background color automatically turns black. Please see the screenshot.

You did not read the Readme. It clearly tells you why this happens and what you have to do to change the behavior.
You could even tell exactly where it is, because there are no troubleshooting guide in the readme.
SideMenuManager.menuFadeStatusBar = false
You could even tell exactly where it is, because there are no troubleshooting guide in the readme.
SideMenuManager.menuFadeStatusBar = false
SideMenuManager.default.menuFadeStatusBar = false
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You could even tell exactly where it is, because there are no troubleshooting guide in the readme.
SideMenuManager.menuFadeStatusBar = false