Font / background for Job Manager Plugin

Ok i’m scratching my head. I have the pixel theme 2.0.2 installed. I just installed Job Manager, and when I posted it, the whole post is blank. As in example here: https://mcmspi.com/blog/jobs-2

Now if you hold down the left mouse button, and drag in that blank box you can highlight the job description. My question is, where do I edit the background color from being a blank white to black so people can actually see the words and my jobs I post?

Thanks in Advance ~