Fig.: to understand someone's feelings and thoughts from his face's expression

He's lying: it's written all over his face

Sta mentendo, glielo si legge in faccia

He keeps saying that everything is OK but, in reality you can tell he's worried about his young daughter moving to a big city like New York by herself. It's written all over his face!

Dice che è tutto a posto, in realtà gli si legge in faccia la preoccupazione per la giovane figlia che deve trasferirsi da sola in una metropoli come New York City

You always know how he will react to something, because he's one who wears his thoughts on his sleeve

Sai come può reagire a qualcosa perché ha sempre scritto in faccia quello che pensa

The audition must have gone badly because when she walked out the theater the disappointment was written all over her face

L'audizione deve esserle andata male perché quando è uscita dal teatro le si leggeva in faccia tutta la sua delusione

It was once a custom for a knight to pin a gift from the lady he loved to his sleeve before going into combat, thus displaying his feelings. Shakespeare uses this expression in "Love's Labor's Lost", where Biron, speaking of Boyet, says, "This gallant pins the wenches on his sleeve," meaning that Boyet is openly devoted to all wenches