/usr/share/gmt/cpt/jet.cpt is in gmt-common 5.3.1+dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 | # $Id: jet.cpt 16562 2016-06-18 04:04:08Z pwessel $
#
# Simulates the JET colormap in MATLAB
#
#----------------------------------------------------------
# COLOR_MODEL = RGB
#----------------------------------------------------------
0.000 0/0/127 0.125 blue
0.125 blue 0.375 cyan
0.375 cyan 0.625 yellow
0.625 yellow 0.875 red
0.875 red 1.000 127/0/0
#----------------------------------------------------------
|