I have just completed the rainbow shell sidequest and recieved the prism dress from melchoir but now i cant get the prism specs or the rainbow from him. Have i done something wrong? How can i get them?

You need to complete the Sun Stone quest as well.

You see, the Rainbow and the Prismspecs are made from an alloy of the shell and the stone.

Therefore, complete the Sun Stone quest, and go see Melchior again.

Also, I'd take the 3 Helmets over the dress any day, but then I'd simply keep replaying until I have helmets for everyone and dresses for everyone, which I was crazy enough to do back when I was a teenager.

okay thanks for the help cause now i am kicking ass.