It is very likely that the person who made the demo (likely Ethan Merritt) has defined his/her own set of default line colors, which are reflected in the demo images. You can do this yourself (see help set linetype
). Example from gnuplot e-mail list:
# Ethan A Merritt - my preference for gnuplot colors
# 2 3 4 5 6 8 are borrowed from the colors_podo set
#
set linetype 1 lc rgb "dark-violet" lw 1
set linetype 2 lc rgb "#009e73" lw 1
set linetype 3 lc rgb "#56b4e9" lw 1
set linetype 4 lc rgb "#e69f00" lw 1
set linetype 5 lc rgb "#f0e442" lw 1
set linetype 6 lc rgb "#0072b2" lw 1
set linetype 7 lc rgb "#e51e10" lw 1
set linetype 8 lc rgb "black" lw 1
set linetype 9 lc rgb "gray50" lw 1
set linetype cycle 9
There are no built-in gnuplot themes, only sets of settings which change colors.
And yes, I do use gnuplot seriously! I use it both for simple plotting and for scientific publication.