I LOVE blue ponies!!
For G1's:
Earth: Nightglider
Peg: Sugar Apple
Unicorn: Starflower
G2: Ivy
For G3:
Earth: Marshmallow Coco (want sooo much)
Peg: Aurora Mist
Unicorn: Whistle Wishes (the only one, such a crime!)
For G4:
Earth: Star Swirl
Peg: Rainbow Dash
Unicorn: Trixie
Fun Fact: My first MLP was a blue pony! (Ruby Lips)