Changing theme

[acmwallace]

So, I want to change the theme on Atom because I have difficulty with the black background. (On OS X)
I went into:
Atom -> Preferences -> Themes
Under "UI Theme", I selected "Atom Light", and the background of the Preferences screen changed. I also changed Syntax Them to "Atom Light". No visible change there, but that seems ok to me.

But when I go back to my code the background is still black, although the syntax colors have changed. What am I missing here? Why doesn't the basic theme change in my editor windows? I closed and reopened the windows, I exited Atom and started it up again, nothing.

thanks,
andy