I prefer bananna plugs for the amp/reciever and angled spades for the speakers.
2: Color isn't critical, but I'd prefer dark, such as black or darg gray. I don't really want to show off or notice the cables. I prefer to focus on the sound! Bright yellow, green, pink, etc would not work for me.
3: Mesh or smooth rubber are nice fine. I don't have a thick cable fetish and as long as they flex and don't hang on corners, etc I'm happy.