adverb/paʁ.le kɔm œ̃.n‿a.vœ.ɡlə de ku.lœʁ/
to talk through one's hat, to speak about an issue one doesn't understand
Synonyms: parler à tort et à travers, parler en l'air
Literally, “to speak like a blind man [would speak] of colors”. Compare Polish mówić jak ślepy o kolorach.