According to your description and attached picture, it is not clear which is the exact element color that you want to change. I have noticed that you found out how to change the color of the RibbonTab but it seems that this is not what you are looking for. So, I suppose that you want to change the color of the content area which is shown when the drop-down is expanded. If you want to achieve this you should access the ContentArea and set some properties:
However, if this does not meet your requirement, it would be greatly appreciated if you can provide more information or a picture of what you exact look should be. Thank you in advance for your cooperation and consideration.
I am looking forward to your reply.
Get quickly onboarded and successful with your Telerik and/or Kendo UI products with the Virtual Classroom free technical training, available to all active customers.Learn More.