I remember it was blue in the first film (as seen when Lennox shoots down Blackout), and then in the sequels they made it red? And before you say “the blue stuff is Energon”, Energon is described by Jetfire to be “the lifeblood of our race”, so it definitely counts as Transformer blood. They should have kept it blue. Not just as a matter of consistency between films; making it red kind of linked them weirdly to humans (why would Transformers have human blood?), as well as looking like MBay was dealing with the “not enough red” complaints.