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-button-title-color: black;
--pocket-minimal-active-button-color: white;
--pocket-button-hover-title-color: white;
}