One of garments of the Kohen Gadol (High Priest) was the Me’il ha-Ephod, the robe.
(לא) וְעָשִׂ֛יתָ אֶת־מְעִ֥יל הָאֵפ֖וֹד כְּלִ֥יל תְּכֵֽלֶת׃ (לב) וְהָיָ֥ה פִֽי־רֹאשׁ֖וֹ בְּתוֹכ֑וֹ שָׂפָ֡ה יִֽהְיֶה֩ לְפִ֨יו סָבִ֜יב מַעֲשֵׂ֣ה אֹרֵ֗ג כְּפִ֥י תַחְרָ֛א יִֽהְיֶה־לּ֖וֹ לֹ֥א יִקָּרֵֽעַ׃ (לג) וְעָשִׂ֣יתָ עַל־שׁוּלָ֗יו רִמֹּנֵי֙ תְּכֵ֤לֶת וְאַרְגָּמָן֙ וְתוֹלַ֣עַת שָׁנִ֔י עַל־שׁוּלָ֖יו סָבִ֑יב וּפַעֲמֹנֵ֥י זָהָ֛ב בְּתוֹכָ֖ם סָבִֽיב׃
(31) You shall make the robe of the ephod of pure blue. (32) The opening for the head shall be in the middle of it; the opening shall have a binding of woven work round about—it shall be like the opening of a coat of mail—so that it does not tear. (33) On its hem make pomegranates of blue, purple, and crimson yarns, all around the hem, with bells of gold between them all around:
מעיל מכפר על לשון הרע אמר הקב"ה יבא דבר שבקול ויכפר על מעשה הקול
The robe of the High Priest atones for malicious speech, as the Holy One, Blessed be He says: Let an item that produces sound, i.e., the bells of the robe, come and atone for an act of malicious sound, i.e., malicious speech.
But beyond the audial symbolism of the meil’s design, there was also a visual symbolism too, which the Chofetz Chaim notes.
The color of the Ephod was techeiles, a greenish-blue reminiscent of the sea and sky, which acted as an indirect nod to the Kisei HaKavod, Hashem’s Throne of Glory.
Not by chance, the Tanna Dvei Eliahu says that the "stain" of Lashon Hara goes up to, you guessed it, the Kisei HaKavod to instigate against the speaker.
(יג) וְנוּכַל לוֹמָר שֶׁזֶּהוּ כַּוָּנַת הַגְּמָרָא דַּעֲרָכִין הַנַּ"ל: כָּל הַמְסַפֵּר לָשׁוֹן הָרָע, מַגְדִּיל עֲוֹנוֹת עַד לַשָּׁמַיִם שֶׁנְּאֱמַר {תהלים ע"ג ט'}: "שַׁתּוּ בַשָּׁמַיִם פִּיהֶם וּלְשׁוֹנָם תִּהֲלַךְ בָּאָרֶץ" פֵּרוּשׁ: אַף שֶׁלְּשׁוֹנוֹ הוּא מְהַלֵּךְ בָּאָרֶץ אֲבָל פִּיו שָׁת בַּשָּׁמַיִם.
וְכֵן אִיתָא בְּתָנָא דְּבֵי אֵלִיָּהוּ {פרק י"ח}, שֶׁהַלָשׁוֹן הָרָע שֶׁהוּא מְסַפֵּר, הוּא עוֹלֶה עַד כְּנֶגֶד כִּסֵא הַכָּבוֹד, וּמִזֶּה נוּכַל לֵידַע אֶת גֹּדֶל הַחֻרְבָּן, שֶׁמַּחְרִיבִים בַּעֲלֵי הַלָּשׁוֹן אֶת כְּלַל יִשְׂרָאֵל.
(13) And we can say that this is the intent of the aforementioned Gemara in Arachin, viz.: "All who speak lashon hara magnify transgression until the heavens, as it is written (Tehillim 73:9): 'They set their mouth in the heavens, and their tongue walks the earth.'" That is, even though his tongue walks the earth, he sets his mouth against Heaven. And thus do we find it in Tanna d'bei Eliyahu (Rabbah Zuta 18) — that the lashon hara that he speaks rises against the Throne of Glory. We can hereby derive some idea of the greatness of the destruction wrought against Israel by the "men of the tongue."