I am sorry to hear you have experienced problems with how your email is displaying. I absolutely want to get to the bottom of this, but I would need some more information:
1. What is the name of the (or a) campaign where you have experienced this issue?
2. What email clients have you seen or contacts have reported the change in background color?
This should give me enough to investigate further and understand what might be going on. If you would feel more comfortable taking it offline, please feel free to email us at social_support(at)constantcontact(dot)com with your username, answers to the questions above, and a reference to this post and we will get to the bottom of it!