I found the source of the problem:
The ability to change the editor color scheme is not in
tools>preferences>syntax coloring
as has been stated in several posts on the subject, but rather in
where a drop-down menu at the bottom of the pane marked "Syntax color scheme:" allows you to change the color scheme.
The syntax coloring pane allows you to change the composition of the color schemes, but does not allow you to apply it.
From the perspective of a non-power-user, this is a bit confusing.