זוהר שמות — דף קלה ע”א

Six materials correspond to six festivals and holy times. Gold corresponds to Rosh Hashana, judgment and the north, silver corresponds to Yom Kippur, the whitening of sins. Copper corresponds to Sukkot where the nations lose power, blue-violet corresponds to Passover and the slaying of the firstborn. Scarlet corresponds to Shavuot, the giving of Torah from both sides, and crimson corresponds to the fifteenth of Av when the daughters of Israel dance in linen garments.