You're welcome Landgrab~
If you wanted to use it online, you would simply have to try replacing one of the existing skybox textures with an old one, though the lighting on starships might look off.
Yeah, if you wish to keep checksum at zero, you can still try partial skybox replacement, by only changing the textures.
The texture .dds go hand in hand with its respective mesh. If there is a mismatch between the texture set and the mesh, you will see graphical glitches. Good news is that some stock skyboxes have virtually identical meshes. Rebellion comes with the following skyboxes:
skybox03 (red nebula, not used by any stars in rebellion.)
skybox04 (green nebula)
skybox08 (purple nebula)
03 04 07 have identical meshes.
02 05 06 have identical meshes.
08 is on its own.
Therefore, to get rid of the green skybox, you can simply copy skybox03environmentcube.dds, SkyboxBackdrop3.dds to your mod. Also, copy skybox06irradiance.dds (03 does not come with irradiance). Then rename them to skybox04environmentcube.dds, SkyboxBackdrop4.dds and skybox04irradiance.dds.
This will replaces the green skybox with red skybox. However, the planets/asteroids colouring is mostly dependent on the definition in SkyBoxProperties.skyboxbackdropdata, which you cannot change if you want to keep checksum at zero. Therefore the planets/asteroids will have a green hue over them (this is true in the latest Bailknight's Graphic Mod).
The ships are also affected by SkyBoxProperties.skyboxbackdropdata, but in my experience, it seems their colour mostly depends on the textures, so they should look quite ok.
It is. It may simply have been unavailable for the star in your system. I do not remember which color Stars can have the green skybox, but perhaps make a map with a green star and do that and you should get it.
In Rebellion, all stars except red use all skyboxes 02 04 05 06 07 08. Red star only uses 02 06 07.