As far as the Black Watch is concerned; the red and white squares of the diced hose were outlined in black for the solders/infantry. Members of the regimental band, such as pipers; wore diced hose that had squares of red and black
The red and white diced hose of other kilted regiments e.g; Gordons, Seforths, Camerons etc, did not have the black outline, but there band members did wear the red and black diced hose.