I've always wanted to know how the save preview/picture is made. Sometimes I see it with DECO, other times without DECO, and a few times i've seen it where some parts have DECO and others don't. Why does it do this, and is there a way to prevent this? Is it possible to make it show ONLY the deco layer?

Sometimes, deco appears gray, even when it's not gray. Example: The red writing on my 50kt nuke appears gray.