Thank you for contacting Telerik support.
The best way to achieve the desired behavior is by modifying the theme that you are using. The described elements use image to paint their fill, so you need to replace the image in their image shape repository with the desired one. The attached video demonstrates how this can be achieved.
You can reed more about how to use custom themes in this document article: http://www.telerik.com/help/winforms/themes-using-custom-themes.html
I hope this helps.
the Telerik team