Where can I change font-color when firebug leads to Domain-name

Hi,
i looked up where I can change the color of my body font (p) with firebug, but instead of many other informations being found in the style.css, it tells me that this information is in the domain-name https://www.foerderverein-rds.de.
Can someone please tell me, where I can change the color then? I′ve been checking all files in my wordpress-folder by searching the name of color (#70706e;), but the only matches I found were customizer.php and customizer-css.php. I changed the color numbers in both, but none of them affected the look after I reloaded the page.
Please help, I spent 6 hours on searching for a solution.
Thanks a million in advance
Lucie