/usr/share/gwyddion/glmaterials/Green-Rubber is in gwyddion-common 2.50-2.
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 | Gwyddion resource GwyGLMaterial
0.0 0.05 0.0 1.0
0.4 0.5 0.4 1.0
0.04 0.7 0.04 1.0
0.0 0.0 0.0 1.0
.078125
|