functions.php

<?php

/**
 * Display Posts Shortcode, add category classes 
 * @see https://displayposts.com/2019/01/03/add-category-classes/
 */
function be_dps_add_category_classes( $classes ) {
  $categories = get_the_terms( get_the_ID(), 'category' );
  if( ! empty( $categories ) && ! is_wp_error( $categories ) ) {
    foreach( $categories as $category ) {
      $classes[] = 'cat-' . $category->slug;
    }
  }
  return $classes;
}
add_filter( 'display_posts_shortcode_post_class', 'be_dps_add_category_classes' );

Thanks for the quick response. While I coded many years ago, I'm still working on CSS. Can the above code be added to the Custom CSS area at the bottom of the CSStyle file? or maybe using the WordPress Customization option for CSS? In your example is "catagory" and "Cat" variables for the category I want to affect? Also where would I set the font size and color in your statement?

I found this code but it doesn't seem to work.
.category-news {
font-size: 18px;
font-style: italic;
}
Thanks Again

there is a typo in the code snippet @ line 11: "$categoriess" should be "$categories"

This code snippet goes in a core functionality plugin or Code Snippets.