Time for an incredible Harry Potter Cake

Harry Potter Cake

No I did not make this cake, but I saw it in the window at Patisserie La Reine in Broadmead in Bristol. I like the book form they have used, and have not gone for a simple closed book, it actually looks like an open book too. They have managed to catch the character of the sorting hat, though does a hat even have character? My only thought was why did they choose that colour?