How to change gutter width and color?

Where do I specify the gutter width and gutter background color (I assume the settings are in or I would add them to styles.css?)? My goal is to configure atom as a plain text editor. I love the look of the Sublime editor but I am not going to pay $80 when all I want is a plain text editor like atom that is highly configurable and customizable. I figured out how to disable the gutter, but then the text I type is right up next to the left window edge; if I could make a narrow gutter with the same background color as the main text entry window, that would solve a problem.

Perhaps there is a theme or should be one that lets people like me quickly make atom into a simple Windows Notepad type plain text editor, with no intention of doing github or computer programming with atom?