Blue
Rabbi Yitzchak here relates how he once saw Rabbi Shimon speaking about the Torah, when a pillar of cloud, and a light within the pillar, appeared from the sky. This same thing, of course, had once been written about Moses. Rabbi Yitzchak goes on to speak of the second day of Creation, whose aspect is blue. On that same day, we learn, Gehenom was created, emerging from the center of the fire, and with it the emergence of black and filth, mire and dirt.
When blue is an aspect of Creation, it is time for judgment. Drawing upon the merit of Moses and the immeasurable Light of Rabbi Shimon, we annul harsh adjudications and decrees that have been set forth against mankind. We shift the entire world to a destiny of redemption that personifies mercy and miracles, for this is the wish, hope, and prayer of Moses and Rabbi Shimon. And that is the great power of the Zohar.