/usr/share/plplot5.9.9/cmap0_alternate.pal is in libplplot11 5.9.9-2ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#ffffff
#000000
#0000ff
#ff0000
#a52a2a
#fa8072
#ffc0cb
#7fffd4
#f5deb3
#40e0d0
#bebebe
#00ffff
#00ff00
#ffff00
#ff00ff
#8a2be2
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