How do we express colour? Different languages have words for many colours. However, a reasonably standard order exists for how the words for different colours are developed. Almost every language has specific words for black, white, and red. Afterwards, languages tend to create words for green and yellow (often only one of them), and then eventually blue. However, this is only sometimes true. For example, ancient Hebrew (and Aramaic) does not seem to have a word for yellow. Instead, they treated yellow as a shade of green (the term "tzahov", translated as yellow from modern Hebrew, probably meant a shade of gold. However, at least two shades of blue are mentioned in the Tanach (techelet, a deep almost sky-shade blue, and kechal, a very dark blue).
The colours were named because they had utility. Each colour that was to be used was given a name. That is especially true of the colours of the Mishkan. The kohanim in the Mishkan wore (predominantly) five colours: zahav (gold), techelet (likely a light blue), dark red or purple (argaman), tola'at shani (bright red), and linen (white). What do these colours mean?
Let's start with the linen. Linen is always white in the Torah (they lacked the technology to dye it, unlike wool). Each Cohen would wear linen breaches (michnasayim), a linen shirt (kutonnet), and a linen turban (migba'at or mitznefet for the high priest). These are the essential clothing of the Cohen. The white linen, in the Tanach as now, represents purity. The Kohanim wore a completely white outfit to symbolise their purity from sin (aspirationally).The other colours carry a different symbolism. The Gemara tells us that techelet (blue) is similar to the sea, which is similar to the sky, which is similar to the throne of glory. In parshat mishpatim we see that when the elders of the Children of Israel see an image of Hashem, it is compared to "the bright spot of the sapphire and purely like the essence of the sky." Blue is a colour of godliness in the Torah.Argaman likely was an intense red, similar to the colour of blood. Aragaman represented our humanity. In the Torah, blood is the seat of the soul. So blood-red threads in the Cohen's clothing symbolised his humanity and his standing as a man, not an angel. Shani was also red but much brighter. The Torah doesn't tell us the meaning of the colour; however, in Yishaya, we are told, "If your sins are red as Shani, they will become as wool (white)." Shani symbolises a state of sin or evil.
Finally, the high priest's clothing also includes gold thread. Gold represents the glory and honour that the clothes of the Cohen were supposed to impart.
Each Cohen wore a belt. Some claim that his belt was only linen, like the rest of his clothing. However, some say it was a weave of techelet (blue), argaman (dark red), shani (bright red), linen (white), and gold thread. Why was a belt woven from all these different colours? The mix represents the Cohen's mission when he serves in the Temple. A Cohen represents us before God. However, he does things that we could never do. A non-Cohen cannot participate in the Temple service in the same way. Instead, we stand to the side and watch as the Cohen atones for us. We pray that he can fulfil his mission without knowing whether he is successful. A Cohen carries a unique set of attributes to be able to serve G-d so on our behalf. On a base of purity, he adds a weave of godliness and divinity, his human nature (as opposed to the angelic side, which he must prioritise when acting in the Temple), the ever-present reality of sin and mistakes, and honour. A Cohen may not perform Temple service while wearing anything but his mandated clothing. If he does, the sacrifice is invalid. The Gemara also tells us that "when their clothing is on them, their Cohanic status is on them, and when their clothing is not on them, their status is not on them." We can understand why by examining the symbolism of the Cohen's clothing.
We are not Cohanim serving in the Temple, and we no longer have a Temple from which to function. However, we can and should replicate these traits. Many of our practices deliberately imitate the behaviour of Cohanim in the Temple. For example, we should wash our hands before praying, similar to what the Cohanim did before bringing any sacrifice. As such, If we start from a place of honesty and childlike purity and then include our divine connection, human inclinations, and even the reality that we will make mistakes, we can use Cohen's clothes as a blueprint to advance in our quest for godliness.
