Setting text color on static front page

Hello, I’m having trouble with a static front page in Rectangulum. The text is white-on-white, with no way to change that in the customizer, and the page title is shown above the text in a large font. I don’t want it to appear there at all.

I made some other static pages which display fine, with readable black-on-white text. It’s only the front page that isn’t working.

I know this will be somewhere in the CSS, but could you do me a favour please and point out where to change the font colour? I don’t know what string to search for.