You don't say how old your tree is, but Colorado Blue Spruce have a tendency to get more green as they get older. They also have a tendency to develop dead limbs along the bottom of the tree. There are named varieties such as Fat Albert of blue spruce that retain their color throughout their lives, but the common one doesn't always stay really blue when they get older. Also, there's no oversight on what's sold as blue spruce and sometimes I've seen regular spruce with a bluish tinge (they often all look kinda blue when young) sold as the real thing, but the plants are not true blue. And finally, the amount of blue a tree has in it is as much a matter of genetics as anything else and in the common blue spruce the amount of blue naturally in each tree can vary a lot. "