Using an existing Sublime 2 color scheme, is there a way to tweak the background color selectively for eg. .js files only? Many thanks!
You have to modify your .tmTheme color scheme plist. You can find it with menu Preferences/Browse Packages..., Color Scheme - Default directory.
You should add something like this:
scope
source.js
settings
background
#000000
as a child of the settings array (of course you have to change #000000 with your color code).