Great question, thanks for posting! You can control the colors in your email using the panel labeled "Colors & Fonts" on the left. You will see each section of your email is labeled so that you can control the headers and backgrounds one at at time. An alternative is to click into each block and use the background color and font color icons here.
Hope this helps,
Hannah M. Community and Social Media Support
If you find my post helpful, and it answers your question, please mark it as an Accepted Solution
Just in case you don't know the exact color code of your logo, you can go to this website (http://html-color-codes.info/colors-from-image/ ).upload your logo and click on the color you want. It will give you the color code and you can input that into Constant Contact when creating a campaign to match it perfectly with your logo. (Screen shots below on how to input into Constant Contact.)
Just thought I'd share in case you or others reading this thread did not know how to find color codes!