basically it is a clouds (noise) texture , blended with sky model - now i need someone to help me with :
1 - get rid of “under horizon” part - i tried to mix with transparent shader using color ramp with alpha but with no luck…
2 - plug in some colors into clouds texture - i have no idea how to change their color…
3 - if anyone can make this sky better - improvements are welcome
ad1 - but clouds are rarely that low - its better to have them start a little above horizon…
ad2 - i will try…
ad3 - grab the blend - this will be easier for you
The color ramp has alpha set to zero on the left marker and 0.5 on the right marker (for example, in this image). That’s the overlay factor for the clouds.
Move the left marker to raise the clouds over the horizon. Move the right marker to affect the transition in between no overlay and full overlay.
I looked a bit into changing the colors of the clouds. Right now, I understand what all the nodes do but I don’t understand the result. When you reroute the noise from anywhere along the branch before the overlay, you get an almost white texture which doesn’t match the result. I must look deeper… and most probably break everything.
That’s it. According to the colors on Pxl666’s image, that’s the new Hosek/Wilkie sky texture like in my version. The colors are much better and you must really increase the strength. That’s all the differences I’ve seen so far…
The “Separate RGB” node is used to access the different components of a vector. Here, the Z value of the generated UV map.
A “Separate XYZ” node dedicated to the vectors is planned but nobody really cares. “Separate RGB” does the job just fine and will keep on doing so for compatibility reasons. So…
When you reroute the noise from anywhere along the branch before the overlay, you get an almost white texture which doesn’t match the result. I must look deeper… and most probably break everything. 
