Thanks! ;-)

Your UI colors can be set in the .ini file.
Here are some examples listed under [view]: (Also within the View and Grid panels in the Options)

BackgroundColor=68,89,96
LockedObjectsColor=150,171,175
SurfaceColorMode=ByStyle
SurfaceFixedColor=192,192,192
EdgeColorMode=Darkened
EdgeFixedColor=187,187,187
EdgeLightenFactor=0.0
EdgeDarkenFactor=0.32
CurveColorMode=ByStyle
CurveFixedColor=0,0,0
LineUnselectedColor=0,0,0
LineSelectedColor=0,255,250
SurfaceUnselectedColor=255,245,245
SurfaceUnselectedTransitionColor=208,255,255
SurfaceSelectedTransitionColor=128,255,250
SurfaceSelectedColor=0,239,235

You can also tweak the aspects of each grid element.

My wife had this cool plastic cutting pad for crafts. It had a grid and a dark color scheme which I went for.
Since Moi's default objects are neutral-to-light shades, a darker background shows them up better.

As for the selected lines, Yellow has always been my least favorite color (yuk!) - so it had to go. ;-)