What's on Denethor's face?

Well, I believe he also was eating cherries and it looks a lot like quả anh đào, anh đào juice.

Chicken has blood.
And also, I'm not sure Denethor eats tomatoes and grapes. It can be any imaginary vegetable hoặc trái cây of Middle Earth.
And Denethor also drinks wine.
Anyway I don't think it matters really, I mean the only point is that it's disgusting and gives bạn a clue about what a dick Denethor is.

Bloody vomit

It looks like blood as it seems to form on his lip rather than actually come out of his mouth. It’s the wrong colour to be cà chua nước ép, nước trái cây hoặc wine, but it is the right colour to be blood

In the scene, it's quite clear that the thực phẩm Denethor is eating is chicken, tomatoes and grapes. I think the writers were going for a metaphor for blood, to hiển thị how recklessly he was endangering his son's life, and they didn't realise that the thực phẩm they'd được trao him shouldn't have red juice. hoặc maybe there was a change between the script nghề viết văn and the thực phẩm placed on set for the actor to eat (though I'm not sure what thực phẩm would resemble blood so well).