Description of the desired feature
It would be helpful if GMT had a way to retain information about the default colormaps for remote files during processing. For example, if the following code produced two images using the geo colormap. This feature would be helpful for PyGMT, where the remote data files are often read into memory before being passed to GMT, resulting in the loss of the default cpt information (xref GenericMappingTools/pygmt#499).

gmt grdimage @earth_relief -R0/10/0/10 -B -JM5c -png ex1

gmt begin ex2 png
    gmt grdcut @earth_relief -R0/10/0/10 -JM5c -Gtest.nc
    gmt grdimage test.nc -B
gmt end show

ex1:

ex2:

Are you willing to help implement and maintain this feature? Yes