Blue
Fred squeezes into his shoulders and rests a thumb to his lips.
"Why the hell would it be blue?" asks the Chosen One, placing his hands in front of the box and pointing to it with his open palms. "Rubber duckies are not blue!"
"I also had them red." The prefect intervenes, in an attempt to calm him down.
Luna lights up and approaches Hermione, "Do they exist in many colors? Are there yellow ones?"
Harry shakes his head, "Are there yellow? Rubber ducks are supposed to be yellow."
George nods and hugs his younger sister, "All the ones Dad has at home are yellow and he'd probably go crazy to know there are blue ones too."
Luna, again, cannot contain her enthusiasm, "Do you have a lot of them? Ginny, you have to show me the collection, please."
"Mom keeps it in a small closet in the living room, which always struck us as odd because she usually threatens Dad with burning all the Muggle trinkets he brings her to the Burrow."
Hermione stares at the rubber ducky that is still in the box-no one has dared touch it until now-and a thought seems to flash through her mind. Fred's silence is then proof that he too is imagining the same thing. She brings her hand closer to the treasure and barely touches it with her index finger: at that contact, she feels the material heat up and instinctively pulls away.
"What the hell did you do, Hermione? It's moving, it's moving!" Ron moves behind Harry's back and clutches his sweater fearfully.
"I just touched it I can't-"
"Dear Molly" a tinny voice sound comes out of the duck's beak and soon adjusts to catch the sound of Arthur's. Fred sighs and nods, a sign that he has really guessed the nature of that treasure. Ginny and George close their eyes and Ron rests his forehead on Harry's shoulder.
"Today is our third anniversary and I love you like it was the first day. I know now, as you look at the present, you're making that face you always make and you think your Arthur darling just can't grow up. The truth is that with you I grow every day and I want to grow with you until the end of my life. Cloying, I know, but I am sure there is a beautiful smile on your face now. I've been working on this surprise for a month, but I'm not that good at spells and I ended up coloring the duckling blue-I don't think Muggles have them blue, also because the ones I give you every year are yellow. This one is special though, it speaks." Here the talk takes a pause and Hermione uses the opportunity to shift her gaze to the Weasley siblings: they have all started smiling and, even she, cannot contain herself.
"I don't even know what the function of a rubber ducky is, no one will tell me. I like to think I have given it a new use: for me the ducks will be a way of saying I love you. You're laughing now, aren't you? I hope it will become a universal language and that soul mates will express their love with rubber ducks and, why not, rubber ducks that are not yellow, too! This one is blue and I hope it will remind you of our years at Hogwarts together."