Change Pinboard comments box color?

I’m using the Pinboard theme, and I love everything except the comments box color. I could just change the font, but changing the font would mean also changing the default font of the blog. I need that to be white. But since the font is white it doesn’t show up on the background of the comment boxes. So basically, when someone leaves a comment it’s white on white, so I need to change the background, not the font.
Thank you ??