Hi Jobou.
We do not provide support in the Pre-Sales Forum, and all other forums are for paid customers.
Changing the background color should be very simple — and you may even already have the correct CSS code for it, but I cannot tell without a link to your site. We would probably be able to provide you such a snippet once you have a paid account and post in the proper forum.
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However, I can give you this bit of advice if you’re just trying to make CSS tweaks — instead of having to follow the Themer’s Guide and create new CSS files: You can add custom CSS code via your child theme’s style.css file or via a plugin like Simple Custom CSS or, my favorite, Jetpack. Jetpack supports regular CSS and the LESS and Sass pre-processors.
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Last but not least, we have a pretty great Refund Policy so you can buy one or many of our add-ons and thoroughly test them.
Let me know if you have any follow-up questions.