Ours has a rainbow collar, too! I love all the pretty colors (this is Rara not Bry lol--he's not so much on the rainbow!)
Bullit had many collars as he was growing he was always getting so big all the time, now he has grown we have a proper staffie collar for him with the brass buttons, I want a pink one for Luna with the staffie knot on when she gets bigger, she had a pink one with diamanties when we first got her but she has grown so she is wearing one of Bullits old ones at the moment which is Blue, so everyone thinks she is a dog not a bitch