You can adjust the following styles. Remove any line to revert it back it’s default value.
/**
* Simple Table
* Text Styling
* From Will-Myers.com
**/
div[data-wm-plugin="simple-table"] {
--simple-table-title-color: white;
--simple-table-title-font-weight: 700;
--simple-table-title-font-size: 1.2em;
--simple-table-value-color: white;
--simple-table-value-font-size: 1rem;
--simple-table-text-align: center;
}