ooh, sure. Use away

But my textures is also cubemap, with 6 discrete pictures. I just changed some colors of the old once and saved them with alpha channel.
So i dunno if it will work for what you have in mind
Also the one i edited is called SkyboxBackdrop7.dds.
And i have no idea what the skybox07environmentcube.dds is for, because even if i change it nothing happens