Hi there!
Thanks for your query!
Screenshots would be better to undersand though, you can change the button style by editing the button itself as follows:
https://prnt.sc/10jw1cz
And if you want to change the gradient color of the default style of button, then you can use the following code in your custom CSS:
:root {
--gradient: linear-gradient(95.55deg, #1a16ff 4.25%, #45ff2f 93.67%);
}
Note: Path towards custom CSS:
Extensions>Templates>Styles>
Click on your current default template name then choose Template Options.
Then find custom CSS within the custom code.
https://prnt.sc/pu705g
https://prnt.sc/pu70zn
Hope this will serve your perpose!
Best Regards