Hi,
Sorry, I was given that specific button code as demo/sample. However, you can try the following:
body .sppb-btn.sppb-btn-default:hover, body .sppb-btn.sppb-btn-default:focus, body .sppb-btn.sppb-btn-default:active, body .sppb-btn.sppb-btn-primary:hover, body .sppb-btn.sppb-btn-primary:focus, body .sppb-btn.sppb-btn-primary:active, body .sppb-btn.btn-primary:hover, body .sppb-btn.btn-primary:focus, body .sppb-btn.btn-primary:active, body .btn.sppb-btn-default:hover, body .btn.sppb-btn-default:focus, body .btn.sppb-btn-default:active, body .btn.sppb-btn-primary:hover, body .btn.sppb-btn-primary:focus, body .btn.sppb-btn-primary:active, body .btn.btn-primary:hover, body .btn.btn-primary:focus, body .btn.btn-primary:active, body .sppb-btn.sppb-btn-primary.sppb-btn-outline:hover{
background: yellow;
}
body .sppb-btn.sppb-btn-default, body .sppb-btn.sppb-btn-primary, body .sppb-btn.btn-primary, body .btn.sppb-btn-default, body .btn.sppb-btn-primary, body .btn.btn-primary, body .sppb-btn.sppb-btn-primary.sppb-btn-outline{
background: blue;
}
It includes primary, default, and outlined peimary buttons.
The following blog may help you to find out the ID/class of your desired elements:
https://www.joomshaper.com/blog/which-line-of-css-i-have-to-edit-code-inspector-in-action
Best Regards