change background for Skydome

pkappetein

How do I change the back for the Skydome?

I added the Skydom DefS (not sure what the difference is between the one without the S at the end)

So the landscape is green.

If I want to make it Night,  I click on the night enviroment or whatever,   I see sometimes what's behind the window in my scene changing,

but upon rending,  the window looks grey everytime,  but inside the ground is changed..   

i don't get it..  

What am i missing here?