The German newspaper ‘BILD’ also takes up the topic.

They write that it is supposed to be methylene blue. Which is of course totally controversial among FIAT cartel doctors.

https://www.bild.de/politik/ausland-und-internationales/robert-kennedy-was-mischt-sich-trumps-gesundheits-minister-hier-in-den-drink-67a55d7b334072169a3e23b8