figure('DefaultAxesColorOrder', [0 0 0; 0.4, 0.4, 0.4; 0.7, 0.7, 0.7], ...
plot(bsxfun(@plus, rand(100, 16), 1:16));
I've omitted the '--' style, because it looks confusing sometimes.
You can set the color style as default for all new figures also:
set(0, 'DefaultAxesColorOrder', ...
To reset it after creating the black and white diagrams:
set(0, 'DefaultAxesColorOrder', 'factory')
I prefer markers in BW diagrams with more than 4 different lines. For a line with 100 points it looks ugly when 100 markers appear. Therefore I've written a LineWithMarkers function, which adds only 10 markers per line. In addition The X-locations of the markers are shifted horizontally to reduce the overlap between the markers.