How to add category name as class to recent_posts container

Hello!
As we are building a global news page where multiple categories are displayed, we would also like to give them a certain “category mood” via CSS. Therefore, we would like to automatically add “the_category()” (so only the name) to the “ish-recent_posts_post” container as a class, to be able to give each category a distinct styling.

Could you please assist in pointing to the right direction, e.g. a filter/hook or template file in order to get this to work? In the end it should look something like:
<div id="rc-post-4307" class="ish-recent_posts_post the-category-name ish-grid12 ish-color7 ish-text-color7">

Thank you in advance!

Kind Regards from Germany!