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 in Exodus 28:31 is indeed blue, which isn't just a fashion choice but a significant symbol within the Hebrew tradition. The color blue was often associated with the divine presence—considered a heavenly hue that ties the priest to God. The robe was woven from linen, providing a tangible link between the ordinary and the sacred, a reminder that everyday life is infused with spiritual significance.

Interestingly, this blue also resonates throughout the Bible. In Numbers 15:38, Israelites were instructed to wear fringes of blue on their garments—a beautiful reminder of God’s commandments. Also, think about how John describes Jesus’s crucifixion attire in John 19:23. His robe, without seams, might echo that perfect blend of beauty and divine purpose found in the high priest’s garments.

It's intriguing how the robes worn by ancient priests and the significant garment worn by Christ connects disparate threads within scripture, painting a larger picture of continuity in themes like sacrifice, holiness, and the representation of humanity before the divine.

And here’s a little trivia nugget: the blue dye used during biblical times was derived from the murex snail, making it an expensive choice. Not surprisingly! It elevates the role of the priesthood to one of royal dignity because only the wealthy could afford such garments. The color thus highlights an overarching theme—the gap between humans and the divine is marked by accessibility, reverence, and a direct path established through sacred mediators!