Hello Nebras ,
Thank you for writing.
In order to achieve this you have to create a custom theme and assign it to
RadMessageBox. Here is a knowledge base article which describes this approach:
Customizing RadMessageBox with custom theme.
If you have any questions, do not hesitate to ask.
Best wishes,
Ivan Petrov
the Telerik team
Q1’11 SP1 of RadControls for WinForms is available for
download; also available is the Q2'11
Roadmap for Telerik Windows Forms controls.