The answer is: Blue

Exo 28:31 - the middle garment, beneath the ephod and above the coat, made from one piece of fabric and similar in design to the robe Christ was wearing at the crucifixon (John 19:23)

The priest's robe, a beautiful garment of blue, held deep significance in ancient Israelite culture. You might be surprised to know that blue, or "techelet" in Hebrew, was a rare color made from a special dye derived from marine snails. This unique hue was associated with purity, divinity, and heavenly connections—quite fitting for a high priest who had the important job of interceding with God on behalf of the people.

When we look at this robe in Exodus, it’s easy to see that the design represents harmony and completeness. Interestingly, it is believed that the workings of the tabernacle and its precious garments mirroring the design of the cosmos highlights a fundamental idea that the physical reality was deemed a reflection of the spiritual realm.

Now, this robe foreshadows the famous robe that John describes Jesus wearing at the crucifixion. Just like the high priest, Jesus had a role fulfilling the connection between the divine and humanity, marking His role as a spiritual mediator.

Quick trivia: High priests wore elaborate attire that includes garments like the breastplate, which had twelve stones representing the twelve tribes of Israel. All these elements not only donned the splendor of God's covenant with His people but also set a powerful precedent in the ages to come about how roles change yet maintain their deeper significations in different contexts of faith and communion. Pretty fascinating, right?