When creating flat side bar panels from code (SideBarPanelItem) you can use following code to apply predefined color scheme to a panel:

SideBar.ApplyColorScheme(mySideBarPanelItem, eSideBarColorScheme.Blue)

You can also use same method to apply predefinied color scheme to whole side bar control as well:

SideBar.ApplyColorScheme(mySideBar, eSideBarColorScheme.Blue)

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