BLUE — specifically a blue-violet dyed wool, and one of the three coloured yarns of the tabernacle (with purple and scarlet). It is the colour of the curtains, of the high priest's robe, and of the single cord tied into each tsitsit at Numbers 15:38 — so one thread of the sanctuary's own colour is worn by every ordinary person. ⚠ The dye is traditionally identified with a secretion of a Mediterranean sea snail, and the identification is a modern RECONSTRUCTION, not continuous knowledge: the source was lost for centuries, and the case for the snail was argued back on chemical and rabbinic evidence together rather than handed down. Worth stating plainly, because the tassels themselves were kept without interruption while the blue in them was not. The shelf renders the cord variously — KJV 'a ribband of blue', ASV 'a cord of blue', NIV 'a blue cord', NWT 1984 'a blue string'. → first discussed at Num 15:38