Hello,

Please remove all the CSS for the button you added and try to use the following selectors and add all the CSS to this.

body .btn-style-link.btn-color-primary.create-account-button {
    color:red;
    border-color:yellow;
}
body .btn-style-link.btn-color-primary.create-account-button:hover {
    color:yellow;
    border-color:red
}

Then check back.

Regards.
Xtemos Studios.