Thank you for letting us know this is happening. Do you know what version of Internet Explorer you are using? It may be part of the problem, only certain versions will work with Constant Contact. You can also try using a different web browser and see if that fixes the issue. Otherwise check out this FAQ about what versions are compatible.
When it comes to color options, you should see an option when selecting colors that says “More Colors”. That will give you almost every option in the rainbow. When you say you would like the option to change individual lines, do you mean the text color or are you looking for more of a highlighting feature? You do already have the option to change the text color, just highlight the text you want to change and select the Font color option to change the text color of just a selection of text.
As far as changing the background of an induvial section, while we do not have that ability at this time I am happy to send the request to the team that works on this editor. I hope that helps you!