Hi Omar,
Thanks for your interest in syncfusion products.
The requirement of changing the RibbonControl styles and themes has been achieved in the below sample. Please have the sample from the below link and let us know if it helps you.
sample:http://www.syncfusion.com/uploads/user/directTrac/109176/CS-977756876.zip
Please let us know if you have any concerns.
Regards,
Paul Anderson S