Color-setting is part of syntax highlighting, because foreground- and background-color have to fit, or your code might partly be unreadable.
Go to "Settings -> Editor... -> Syntax highlighting", chose the filetypes you want to change color for, change the background color for "Default".
The most other keywords use the default background, except for some special cases, like "Active line ...".
Afaik you will have to do that for every set of filetype you use.
