The color blue is a unique color within the spectrum of Judaism. In the Torah, the Israelites were commanded to put fringes, tzitzit, on the four corners of their garments and to weave within these fringes a “twisted thread of blue (tekhelet)”. The reason why blue is used on the fringe (tzitzit) is to help remind us to do the commandments. Many items in the Mishkan, the portable sanctuary in the wilderness, such as the menorah, many of the vessels, and the Ark of the Covenant, were covered with blue cloth when transported from place to place and worn even on the High Priest’s clothing.
Mystical Biblical Blue
In ancient tradition the Holiest shade of blue was revealed on the Day of Atonement [Yom Kippur] when the Al-mighty blessed the waters, the sky and the universe. And most mystically, it was in the vision of the Al-mighty that Moses and the elders saw. “Under His feet was the likeness of sapphire [deep blue] brickwork, and it was like the essence of the heaven in purity” [Ex 24:10]. “Under His feet was the likeness of sapphire brickwork.” “You will hearken” when you see the blue fringe. “You will sanctify” when you use this color on the High Priest’s garment and other holy places, and “you will be ensnared” if you focus on this color in meditation and visions. The gematria of the word “blue” [in Hebrew, 'techelet'] [see Ex. 24:6] is the same as the gematria of the word “you would hearken [in Hebrew, 'shematem]” [Gen 42:22]. It is also the gematria of “and sanctify them [[in Hebrew, 'vekidashtam']” Ex 19:20] and “you shall be ensnared [in Hebrew, 'tinakesh']” [Deut 12:30].
In visions and the most mystical dealings we always seek the revelation of God, which is formless, and singular. Staring at this colour aids in mediation, bringing us a glimpse of the “pavement of sapphire, like the very sky for purity”, which is a likeness of the Throne of God. (The Hebrew word for glory.) In the case of blue, we find that although it is found in so many holy places, when it comes to dreams and visions we are strictly warned, “All colors in visions are a good omen except for the color blue. It is the low color, and much ardent prayer must be exercised to avoid it.”
Even in most holy visions, blue is the lower color or sick color in visions. How can blue be holy and also be called low and sick? The human eye cannot see the actual light, but when we bend the light through a prism we see the spectrum of its colors. There is one light and seven colors. Blue is the lowest color on the spectrum. Blue reminds us of the ocean and of the sky. These are two elements that we cannot live without. But they are also two elements that we cannot live in.
In ancient days, the blue thread was made from a dye extracted from a Mediterranean snail called the chilazon. “Blue is the color of the sea, and fish live in the sea, and fish never close their eyes. So this color must provide protection from the ‘evil eye.’ (This also is why fish are a common motif in jewelry and artwork.) Thus reason why some people paint blue on gravestones and their homes is because they see this to be “protection from the evil eye.” Blue is also commonly found painted on the gravestones of righteous people in the mystical city of Tzefat. Also some homes there are painted blue.
Maimonides claimed that this blue was the colour of “the clear noonday sky”; Rashi, the colour of the evening sky. According to several rabbinic sages, blue is the colour of God’s Glory.
Further references: [Numbers 15:38. Exodus 24:10; Ezekiel 1:26 Numbers 4:6-12]