Rätsel №111263

Oh, how fortunate that the solution of this puzzle as a prize, you can get the blue potion. This is an allusion to the wreath of blue roses, which puts on a Slane on the head of a sleeping Princess. Furthermore, the very anime Aldnoah starts with arguments about why the sky is blue (and ends the same).
And blue potion is one of the components of the recipe for sticker from Slane made to birthday Grandgames