Why is the lucky charm object colored? Usually only Miraculous-related things are. Did Tikki make a Kwagatami for Marinette and hand it off to Plagg, who gave it to Adrien, who worked it into his gift? If so, I hope it makes her extra lucky -- she's going to need it when Befana shows up.
Lucky Charms have never been the only thing that’s been colored and more items will be added, either to impart an idea (Like Chat Noir/Maotif’s eyes glowing in the dark or Marinette wearing the ring being a different color), or to highlight an important item (like the charm bracelets or Adrien’s scarf). The charms I colored because they are a reoccuring item and the scarf and Adrien’s hair I colored because if I didn’t you wouldn’t be able to identify the scarf as That Special Scarf or identify that Adrien’s hair was temporarily dyed.
As for the kwagatama: guess we’ll have to wait and see.