My favorite medium blue iris is Merchant Marine.
It is vigorous, has good branching, blooms heavily and long, and stands up well to rain. Its parent, Yaquina Blue, is also a beautiful medium blue self, a big, robust iris.
A medium blue that is not a self which I recommend is Money in Your Pocket.
This third year clump made quite a statement in my yard.
I agree with the other posters that the best light blue is probably Absolute Treasure, but I grow another light blue that is reliable and vigorous:
Neptune's Cloak (Hager 1992)
