Is there any way to change the gutter back- and/or foreground (and border) color? On my monitor at work I hardly see it and I would like to change it.
Or should I make this into a feature request?

Gutter color follows Look and Feel rules in case if Office11 style selected or System-wide color for Button Face color (see 3D objects).

Since modifying the 3D Objects settings didn't seem to do anything I guess I have that Office LnF selected - can't seem to find where you select that.
Can you direct me to where I need to be to modify those colors please?

uncheck View->Office11 look and fill and system colors will take effect.