Just think about Young Teddy Lupin finding Tonk’s old Hogwarts uniform and walking up to his gran with the robe on and she has just stares at him because although people say he looks like his father more, she sees more of her daughter in the young boy.
Then the first day of Hogwarts comes and Teddy gets sorted into Hufflepuff and he can’t believe that he got sorted into his dream house no matter what other students say about it. He sends and owl to his gran straight away and a few day later he receives a letter and a package. The letter just says how proud his gran and Harry is of him and how she sent what he asked for.
He opens the package to find his mum’s old uniform, robe, tie and scarf that his Gran kept all these years. He doesn’t mind that it’s faded a bit and it has a few pin holes in from Tonks keeping he badges on it for various bands. In fact, one of them is still there on the front and Teddy refuses to remove it.
He changes into it instantly because wants to have something that always reminds him of the stories he heard about Tonks at school. He looks down and finds a single blue hair. He sends and owl to his gran and asks about the hair and she replies back about how Tonks had it for a short while because it was his grans favourite colour.
Next time he visits his gran for the holidays she has a tear in her eye as teddy walks up in the uniform with short blue hair, just like his mother had years before him.