紅也不紅 Not Even A Flush
老魔放下鍾道：「不吃了。這酒常時吃兩鍾，腹中如火；卻才吃了七八鍾，臉上紅也不紅！」老魔放下钟道：「不吃了。这酒常时吃两钟，腹中如火；却才吃了七八钟，脸上红也不红！」
逐句解 Line by line
The old fiend set down the cup: "I will not drink any more."
Five characters of surrender, and the demon does not yet know what he is surrendering to.
"Ordinarily two cups of this wine and my belly is like fire;"
中 is plain zhōng, inside. And the observation is a drinker's: he knows his own capacity for this stuff to the cup.
"and just now I have drunk seven or eight and my face has not so much as flushed!"
紅也不紅 — red and not red — is the identical vernacular formula the chapter used when the sabre failed to redden Wukong's scalp. The two halves of this speech very nearly join into one unit: the first halves are both seven characters and strictly matched. What separates them is that the second half runs two characters longer and closes the quotation.
The demon has correctly identified an anomaly and drawn precisely the wrong conclusion from it, which is what every chief in this cave has done all afternoon. His face is not flushed because he has not had any wine. He concludes that the wine is weak.
It is the same reasoning that met the weightless bottle. Presented with evidence that something has been removed from inside a container, he reasons about the container. The book has run this gag three times now and has not once explained it.