Background color in code

I’m new to all this, so I’ll need concrete answer.
So, I got a code for my newsletter template. Everything works fine except one thing:
My background is black, probably (as I can see a colored table with [content] in it. When I receive newsletter in Mozilla Thunderbird or Outlook everything is fine. But newsletters that are sent to gmail or yahoo are with white background. Do I need to input something else in my code or what?
Thanks you

@dabes some of the web mail providers limit the css styles that they display so this isn’t a problem with phplist. I don’t think that there is much that you can do about it.

Thank you for quick answer.