Hi Maher,
Thank you for writing.
There is no such built-in property for the hover fill, but you can subscribe to the MouseLeave and MouseEnter events of the button and set the color there (in the mouse leave the styles are reset):
If you change the color in Visual Style Builder it will apply for all buttons that are using this theme.
Let me know if you have additional questions.
Regards,
Dimitar
Telerik
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