How do I change the page/post background colour?

Hello, I have just installed the Casinotown theme with the Flytonic framework.

There are no options in the backend of the framework (nor can I see anything in the child theme options) to alter the background colour or text colour of the pages/posts – which is currently back, with grey text.

I would like black text on a white background but I have no idea how to do this.

Do I need to do something with the CSS? I don’t really understand what CSS is, so I have been reluctant to mess with it for fear of breaking something.

Thanks.