Maybe in the moi.ini ?

Change line 61 (or thereabouts) in the Moi.ini file:
LineUnselectedColor=255,0,0
This will give you red dashed lines, nice for the grey background...

I found a solution that suits me by changing the default color, the opacity of the hidden lines as well as the color of the edges.
Options> View and moi.ini

Thank's Death, sure nice color

Pilou, nos messages se sont croisés, le temps que je fasse mes bidouilles et trouve la bonne traduction (google me fait des trucs bizarre quelquefois).