I had never heard of galangal being referred as blue ginger, so I could be mistaken, too. I was simply taught to treat ginger that is marked with a blue ring differently. It can't be grated for its juice, for example.
Here's another type of ginger. It's called "young ginger," sometimes "spring." It, too, is different. For starters, its skin is edible. It's much more mild, virtually no fiber. Raw, its texture is more like a raw potato. Its gingerness creeps up from the back end of the palate. Grating yields a lot of liquid; a slice steeped in tea is one common use. This is also the ginger that is pickled into gari
that is served as a palate cleanser at sushi restaurants.
I don't know if it is actually an immature ginger lily rhizome. I suspect instead that it comes out this way due to a different growing method, perhaps hydroponically. It might be hard to find, even at your local asian market. I don't use it often, so any suggestions for this type of ginger is also welcome.