This is the 3477th most frequent Japanese word.
真っ赤
Bright red; completely red.
Here, "真っ赤" is used to describe the vivid red color of the sky, emphasizing its intensity and brightness.
その空は真っ赤だった。
The sky was bright red.
In this sentence, "真っ赤" signifies the intense red color of a person's face due to an emotional reaction, such as embarrassment.
彼は恥ずかしさで顔が真っ赤になった。
His face turned bright red out of embarrassment.
Here, "真っ赤" metaphorically intensifies the term "嘘" (lie), implying that the lie is completely false and obvious.