Many years ago I harvested cones from some Cedrus atlantica, 'Glauca' in the Fall. I put the cones in paper bags and put the bags in the garage for the winter. The cones opened up and released the seeds. The seeds were then planted in the Spring in a raised bed 3 1/2 ft. wide. All came up green. Apparently the trees that I obtained the cones from were grafted. I did it the next year and the results were the same.
I'm surprised you have closed cones this time of year. Where are you? Australia?
Mike

Algeria, "Belezma National Park" to be specific, original home of Blue Atlas Cedar Trees.

While on the one hand Deodars tend to get less blue with age Lebanese cedars tend to become more silvery. So it seems possible Mike's seedlings might have become fairly blue if he had grown them on for some years - notice how in the pictures here the small Atlas cedar shown first looks green but the older trees in the other pictures have quite a bit of blueness. And the three kinds of Mediterranean region cedars are more of a piece, with the Deodar being the different one.

Forgot to mention that Blue Atlas Cedar Trees here grow in altitudes between 1200 m to 2000 m above sea level.

I should have kept a few. I had several hundred and sold them when they were about chest height. It would have been nice to have a few blue ones.
Recently the Atlas Cedars in my area near Seattle are looking sick. They are losing their needles. Not all, but a lot.
Cedrus deodara do just fine.
No experience with Cedar of Lebanon.
Coincidentally, I friend removed an Atlas Cedar yesterday because it looked so bad and gave me the wood. Here's a picture of it in my truck after I unloaded half of it. The other half is waiting for me. :-) At least I will be splitting it while the weather is still cool.
Mike

Recently the Atlas Cedars in my area near Seattle are looking sick. They are losing their needles. Not all, but a lot

http://pnwhandbooks.org/plantdisease/cedar-cedrus-spp-needle-blight

why does it look different from the one in North Africa?

The cones open after prolonged exposure to winter snow and frost.

This can best be imitated in the home as follows:

1. Soak the cones in an ice-water mix, or water refrigerated at below +2°C, for 3-4 days.

2. Snap the soaked cones in half. If you can't do so, continue soaking in iced water for a few more days until they soften enough for you to snap them (and try putting the cone in a vice, and hit the top off with a hammer).

3. After breaking the cone, pull the scales and seeds off the central stem.

4. The seeds are ready to sow right away. Use a well-drained sandy soil mix, and keep the seeds well-spaced apart (ideally one seed per pot) to prevent any fungal diseases from spreading from an infected seedling to others.

Resin

PS if you have any surplus wild origin cones, I would be interested in some for my study herbarium ;-)

Thnx Resin, I might be able to get some but I'm not sure about shipping them.