Thanks for the answer, solved the problem.

@[Symmetry] / It's a new texture of garry's mod you were to go in its content of garrysmod.vpk but for the skybox is more complicate the color of the
is bound by garrys mod and if this is not the case I publish it soon SFM.

list textures:
gm_construct/flatgrass_2.vft/vmt
gm_construct/construct_concrete_floor.vtf/vmf
materials/maps/gm_collineflatgrass/cubemapdefault.vtf/vmt

Hey, great map! I am trying to use it in SFM, but all the textures are missing, so I see these purple-black textures. Could you please propose a solution?

The console in SFM says this:

material "gm_construct/flatgrass_2" not found.
material "gm_construct/construct_concrete_floor" not found.
"materials/maps/gm_collineflatgrass/c1069_1875_2.vtf": can't be found on disk
Texture 'maps/gm_collineflatgrass/c1069_1875_2.hdr' not found.
Couldn't get HDR 'maps/gm_collineflatgrass/c1069_1875_2.hdr' -- Trying non HDR 'maps/gm_collineflatgrass/c1069_1875_2'
"materials/maps/gm_collineflatgrass/c1069_1875_2.vtf": can't be found on disk
Texture 'maps/gm_collineflatgrass/c1069_1875_2' not found.
"materials/maps/gm_collineflatgrass/cubemapdefault.vtf": can't be found on disk
Texture 'maps/gm_collineflatgrass/cubemapdefault' not found.
Failed, using default cubemap 'engine/defaultcubemap'
Map gm_collineflatgrass missing stringtable dictionary, don't ship this way!!!