/usr/share/gnuplot/gnuplot/5.0/colors_mono.gp is in gnuplot-data 5.0.5+dfsg1-6+deb9u1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 | #
# Provide a consistent set of four distinguishable
# black line types.
# NB: This does not work with "set term post mono"
#
unset for [i=1:8] linetype i
set linetype 4 dt 1 lw 2 lc rgb "black"
set linetype 3 dt 3 lw 1.5 lc rgb "black"
set linetype 2 dt 2 lw 1.5 lc rgb "black"
set linetype 1 dt solid lw 1 lc rgb "black"
set linetype cycle 4
#
set palette gray
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