Hi Mohit Vijay,
The easiest way to achieve this is to use Expression Blend. When you add the RadMenu to your page, navigate to the Resource tab of the project. The name of the Background brush is RadMenuTabBackground.
Attached is a screenshot of the simple project demonstrating this kind of approach. To remove the space between RadMenuItems you can set some negative margin. If you need some more explanation, do not hesitate to contact us.
the Telerik team