/usr/share/gwyddion/gradients/Red is in gwyddion-common 2.47-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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Gwyddion resource GwyGradient 0 0 0 0 1 0.5 1 0 0 1 1 1 1 1 1