One of the special garments worn by the kohen gadol was the robe – me’il – which was lined with bells along its bottom, such that the kohen gadol produced a ringing sound as he walked. The Gemara (Zevachim 88b, Arakhin 16a) comments that the kohen gadol’s robe served as a source of atonement for the sin of lashon ha-ra – negative speech about other people. The sound produced by the me’il signified the rectification of the forbidden “sounds” made by people who spoke negatively about their fellowmen.
It has been suggested that the color of the me’il may also be understood on the basis of this association between the me’il and lashon ha-ra. The Torah requires that the me’il in its entirety be dyed tekhelet, a color which the Gemara in a different context (Sota 17a) says resembles the blue of the ocean and the blue of the heavens. The way we rectify the sin of lashon ha-ra is through tekhelet – by seeing the world from the perspective of the “heavens,” from a bird’s-eye view. If we look closely enough at any person, any group of people, any institution, or any event or experience, we will find what to criticize. If we dig deep enough, we will find something negative to disseminate and protest. So much of the lashon ha-ra that is spoken results from the natural tendency to scrupulously examine and judge, to run a magnifying glass over the people around us in search of a blemish that we can then condescendingly trumpet. The symbolism of the me’il, as understood by our Sages, involves, in part, the message of tekhelet, of stepping back and viewing people from a distance, rather than delving into their characters to identify their flaws.
And thus the me’il provides atonement for lashon ha-ra, by alluding to us the way to avoid it – by ensuring the perceive people from afar, in their totality, seeing the entirety of their characters rather than nitpicking to find their deficiencies.