Another Zanpakuto idea that just came to me. it's a water type zanpakuto named Mizu no Hahen which translates to water fragment or water shard (literally fragment of water)

It's shikai command is michishio(flow), Mizu no Hahen!
In it's shikai (pictured above) the color of the back of the blade changes based on the users mood varying from the blue-gray above to cobalt to sky blue. Yes always a variant of blue, no not as far as purple. It is capable of using water in all three states, ice, liquid, and steam making it capable of freezing, drowning, and flash-frying someone.
It's bankai is Chou no Mizu (butterfly of water).