The Greek goddess of health was Hygeia, which the word 'hygiene' derived from. She was the daughter of the medicine god Asklepios and sometimes attendant to Aphrodite, the goddess of beauty and love.
Iris is the goddess of rainbows. She is also called the messenger goddess, but Hermes is the messenger god, so she is first and foremost the goddess of rainbows.
There are several songs that reference Greek mythology. Here's some that i know of: "When You Sleep" by Cake "Land of the Dead" by Voltaire The album Intimacy by Bloc Party contains more than one...