OK, favorite poses:
G1: Sugarberry Pose. The pony I have in this pose is Scoops. I love how this pose seems to make the pony look confident since they're standing up tall. Even this pose alone make Scoops one of my favorite G1s (that I actually own).
G2: I don't know. I don't have any aside from my McD Sundance. I'll just say all of them.
G3: Donkey Pose.
It's just so funny that I can't resist it. The ponies I have in this pose are Jazz Matazz, and McD Pinkie Pie and Minty.
G3.5: Out of all my G3.5s, I only see two poses (unless you count the fact that Sweetie Belle uses a smaller mold). I'll have to say standing pose.
G4: Standing Pose. I'd choose walking pose, however, the walking pose ponies can't fit in the driver seat of Pinkie's car!
Colors:
G1: I love white G1s for some reason. So pretty. I also like Shady's blinding color body, but I won't choose it since I don't have her yet. Oh, and I don't have Twist either, but her dark purple body is amazing.
G2: Blue ones are pretty!
G3: Blue. Two of my fave G3s are blue (Waterfire and Sea Spray).
G4: White. I love Blossomforth and Plumsweet.