Luke is at risk of vitamin deficiencies because of his hemodialysis, which removes many water-soluble vitamins and trace minerals into the dialysate. Despite his need for extra vitamins, what vitamin supplement should be avoided because of the effects of reduced kidney function on rising blood levels of the vitamin

I'm pretty sure it's Vitamin A

answer:

i don't believe the ocean is purple, but it might once have been:

as for the sky, according to nasa:

"sunlight reaches earth's atmosphere and is scattered in all directions by all the gases and particles in the air. blue light is scattered more than the other colors because it travels as shorter, smaller waves. this is why we see a blue sky most of the time."