expression, nidan verb (lower class) with 'ru' ending (archaic)
what you believe in your heart is revealed in your face
Proverb meaning that one's inner thoughts and feelings naturally show on one's countenance. Archaic verb form あらわる (modern あらわれる).
「心内にあれば色外にあらわる」というように、彼の不安は表情に出ていた。
As the proverb says, 'What you believe in your heart is revealed in your face,' his anxiety showed on his face.
Modern equivalent with the same meaning, using the modern verb 表れる instead of the archaic あらわる.
A classical Japanese proverb. The exact origin is uncertain, but it reflects a common belief that inner character is reflected outwardly.