RadForm has AllowTheming property which enables/disables the aero effects of RadForm and when you set it to false our theming mechanism is disabled. Add a property,e.g. ThemeResolutionService.ApplicationAllowTheming, which will control the AllowTheming of all forms in the application. In addition, RadForm should have a new property,e.g. EnableApplicationAllowTheming, which will control whether the respective form should respect the global property or not.

Case 1: 
ThemeResolutionService.ApplicationAllowTheming = true
RadForm1.EnableApplicationAllowTheming=true //this property is set to true; this indicates that the local AllowTheming property WON'T be respected and the global property ApplicationAllowTheming  takes effect
RadForm1.AllowTheming=false

RadForm1 has theming.

RadForm2.EnableApplicationAllowTheming=false //this property is set to false; this indicates that the local AllowTheming WILL be respected and the global property ApplicationAllowTheming  DOESN'T take effect
RadForm2.AllowTheming=false

RadForm2 doesn't have theming.

Case 2:
ThemeResolutionService.ApplicationAllowTheming = false
RadForm1.EnableApplicationAllowTheming=true //this property is set to true; this indicates that the local AllowTheming property WON'T be respected and the global property ApplicationAllowTheming  takes effect
RadForm1.AllowTheming=true

RadForm1 doesn't have theming.

RadForm2.EnableApplicationAllowTheming=false //this property is set to false; this indicates that the local AllowTheming WILL be respected and the global property ApplicationAllowTheming  DOESN'T take effect
RadForm2.AllowTheming=true

RadForm2 has theming.

Note: the same logic is implemented for the ThemeResolutionService.ApplicationThemeName: http://docs.telerik.com/devtools/winforms/themes/using-a-default-theme-for-the-entire-application