code snippet

[petrasovaa]

I suggest to remove all env=env and **kwargs to keep it simple, these are implementation details. Also the color rules could be rewritten like here (into separate list):
https://grasswiki.osgeo.org/wiki/Using_GRASS_GIS_through_Python_and_tangible_interfaces_(workshop_at_FOSS4G_NA_2016)#Computing_slope

it will look little bit better.