Thank you for writing.
I managed to reproduce the issue according to your description. When the buttons in RadCommandBar are protected and the form is inherited in the child form all buttons settings are serialized, thus the buttons have those settings as local settings causing them to loose their theme settings. I am logging this issue in our Public Issue Tracking System
and we will address it in a future release. Feel free to add your vote for the issue here: http://www.telerik.com/support/pits.aspx#/public/winforms/12362
The work around is to make the command bar protected and make the buttons private again. Then expose the buttons as properties of the main form so you can access them from the child forms. Unfortunately, you will not be able to work with them in design time of the child forms.
Your Telerik Points
have been updated for this report.
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I hope that you find this information useful.
All the best,
the Telerik team