Beautiful.
Some say blue spruce make lousy bonsai...
That's true, some do say that, and some used to say that Mugo Pines make lousy bonsai. Both trees however fall into the category of effort. Blues are difficult because they do not respond to wiring with submitting immediately. They take constant wireing for years before some branches will stay where you put them. Also they are very picky, as my wife would say, and can be painful to work with, kind of like making a bonsai out of a roll of concertina wire.
In the USofA the Mugo, being a common landscape tree not found often in a configuration recognizable as a bonsai, are avoided because the work to transform one of these trees is long and takes some fore thought. In other words many consider this more work than they want to invest. So the tendency is to condemn the two trees as lousy bonsai rather than to admit that there is an unwillingness to take them seriously.
The European masters have pretty much dispelled the Mugo myth by using harvested natural dwarfs. The Colorado Blue still needs someone to do the same. I know there are a lot of specimens available out there in the woods but none seem to be making their way to the growers tables. I suspect mostly because many consider them a waste of time---something I guarantee is not true. I think there is a real possibility for this resource. It kind of reminds me of the old Gold rush days in Colorado where the story goes that many went to find gold but were hampered by this stubborn, sticky blue clay that cloged up everything and made getting the gold out very difficult. Someone had the idea to analyze this goo and discovered that it was high grade silver ore and so was born what was to be called The Com-stock Load, one of the richest silver discoveries in history.