/usr/share/plplot5.9.9/cmap1_lowfreq.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.
1 2 3 4 5 6 | v2 hls
4
0. 240. 0.5 1.0 1. 0
0.499 240. 0.5 0.0 1. 0
0.501 60. 0.5 0.0 1. 0
1. 60. 0.5 1.0 1. 0
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