For a while I've been trying to "delete" the sky so that the fog is much more realistic (When it's foggy for real you can't see a blue sky now can you?)

The simple stuff sort off worked so on a "clear" day both fog and sky are white and no stuff are popping up from the sky.
The problem is that I can't make the day match the night since the night seems to use the same sky texture as the day.... the night sky is now partly white (only the fog has turned to black)

So how can I make the sky look tottaly black now?

Further... is there a way to see wich exact color the blight and sandstorm fog is, so I can give the sky the same texture? since I doubt the blight fog is also white...

I don't have any idea about your other question and I'm not really sure I get what you're trying to do, but fog RGB values are in the ini under the weather sections.

The newest version of MgeXE doesn't draw the skybox when exponential fog is turned on. If I'm understanding you correctly this is want you want.