真っ青

1. Origins, structure, and basic meaning

• Structure: Written 真っ青 and read まっさお, it means intensely blue and also describes a face going pale from shock or fear.
• Basic usage: It appears in a cloudless deep-blue sky and in someone's reaction to losing a wallet.

2. Common pitfalls and similar expressions

• Color versus shocked complexion
  • With a person it exaggerates loss of color rather than literally turning the skin blue.