You can adjust the following button styles. Remove any line to revert it back it’s default value.
/**
* Pocket View
* Button Styles
* From Will-Myers.com
**/
[data-wm-plugin="pocket-view"] {
--pocket-content-border-width: 5px;
--pocket-content-border-type: solid;
--pocket-content-border-color: black;
--pocket-content-border-radius: 25px;
--pocket-content-padding: 20px;
--pocket-content-container-background: white;
}