It is not in the Talmud but rather the Zohar!See:Soncino Zohar, Vayikra, Section 3, Page 102a ‘On this day the priest is crowned with superior crowns and stands between heavenly and earthly beings and makes atonement for himself and his house and the
priests and the sanctuary and all Isr...ael. ............ Isaac said: ‘A cord was tied to the feet of the High Priest before he entered the Holy of Holies, so that if he died suddenly within they should be able to draw him out. They used to know by a certain thread of scarlet if the priest had been successful in his intercessions. If its colour did not change, they knew that the priest within was not free from sin, but if he was to issue in peace, it was known by the thread changing its colour to white, when there was rejoicing above and below. If it did not, however, all were distressed, knowing that their prayer had not been accepted.’ [Tr. note: v.. T.B. Yoma, 39a.] R. Judah said: ‘When he went in and closed his eyes so as not to see what he had no right to see, and heard the voice of the Cherubim chanting praises, he knew that all was in joy and that he would come out in peace, and another sign was if his words came forth joyfully, so as to be accepted and blessed."
But there does not appear to be any other source to confirm this...Also from Wikipedia:The Zohar is mostly written in what has been described as an exalted, eccentric style of Aramaic, which was the day-to-day language of Israel in the Second Temple period (539 BC – 70 AD), was the original language of large sections of the biblical books of Daniel and Ezra, and is the main language of the Talmud.Jason Robillard