It seems to have partially inherited fonts and colors from my current settings, which has made it pretty ugly right now. I looked in fonts and colors but there is no settings for C# Interactive.
Disclaimer: I work for Microsoft on the Roslyn team.
We have not done the polish work to create the logical and correct fonts and colors for the C# Interactive Window yet. In this case, the black text in your screenshot should using Text Editor->Plain Text, but it's not. Instead, it's using "Text Editor->Interactive Console - Black". If you change "Text Editor->Interactive Console - Black" to match your "Text Editor->Plain Text" setting, it should look much better.
In the June 2012 CTP you can set the C# Interactive Window output fonts & colors using the following under "Text Editor":
Roslyn - Interactive Window Error Output
Roslyn - Interactive Window Output
Input fonts & colors are governed by the normal text editor settings.
来源：https://stackoverflow.com/questions/8155616/is-there-a-way-to-change-fonts-and-colors-for-the-c-sharp-interactive-window-in