/usr/share/gmt/cpt/red2green.cpt is in gmt-common 5.2.1+dfsg-3build1.
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 | # $Id: red2green.cpt 12822 2014-01-31 23:39:56Z remko $
#
# Like POLAR, but red to green instead
# Designed by P. Wessel, SOEST
#
-1 red 0 white
0 white 1 green
|