I'm in with Bruce in that cement backer board (durock or wonderboard, etc) should be used wherever tile is to be installed, whether it be in a wet area (shower/tub surround) or dry. I don't recommend tile over any drywall for any reason. It can be done, it is done, but it's more prone to failure and much more difficult to repair should repairs ever be required.
Blue board is typically used for veneer coat plastering. Unless you're plastering, I'd avoid it. Green board is MR, or moisture resistant, and is commonly used in bathrooms. Note the word "resistant" and not "proof." Water can still damage green board, but it does "resist" water penetration better than standard gray-papered board.
Green board is NOT designed to go on ceilings. due to the additives that make it MR, it has less strength and can sag. It can be put on ceilings, but ensure that the framing is not greater than 12" oc.
I recommend: 1) Cement board wherever tile will go: walls, floor, ceiling. 2) MR board on the rest of the walls in the bath. 3) Either 5/8ths inch regular drywall on the ceiling, or MR with framing 12" oc or less. 4) All drywall, whether green or gray, should get a high-quality primer and paint designed for high-moisture areas like bathrooms. Consider a mildewecide additive in the paint as well.
All tile goes on the cement board with modified thinset. No mastic.
Lastly, ensure that you have sufficient ventilation with adequately sized (diameter AND length AND not too many bends) duct work to vent the bathroom.