It really should coordinate with the outfit, setting, and a person's coloring. For example, a sparkly polka-dot pink My Little Buttplug would probably not work too well in a leather fetish dungeon.

Also, I would think a Kaitou Kid buttplug would have more of a BabyJesusPlug look-- a rounded "top hat", a band of blue, a ridge, a face carved in shallow relief, and the flared bit would be the shoulder caps and the tie would be the wire to the control.

... Hakuba would like it?