Water's just water and not earth (soil, sand, grass, etc). I don't know. To me, blue won't fit with the earthiness of the other two cases, but at this point I doubt I really care.
No, no. I think ScottR was on to something there. To me at least, the theatrical edition keepcases are slightly metallic dark green and maroon. So if it is blue, then it may as well keep in that tradition.
Gold would look quite kingly. It looks to be blue, but gold definitely would be great. A nice, earthy gold. Very attractive. :) Blue, on the otherhand, might look good, but can look all wrong. There's light blue which would be too cheery and isn't the tone of the movie. Dark blue could look...