extremely nitpicky gripe, but making leaves and flowers blue using food colouring was something I actually did, in kindergarten, so the line about "not being able to make the leaves blue" threw me off. it's a hell of a lot easier than making meat blue. plus, plants were traditionally a source of blue dye.
also, House of Leaves, anyone?
Except he was furious that Augustus was touching the chocolate river and he was even more upset that he fell in it, presumably because that batch is effectively ruined.