This study documents, though it cannot fully explain, the striking shift in the spectrum of colour patterns in woollen textiles, from those of the Black Death era in the mid to late fourteenth century to those of the fifteenth and the first half of the sixteenth century, in the southern Low Countries: a radical shift from bright red and vivid colours, especially scarlet, or mixed colours (in medley and striped woollens) to much darker, blue-based colours, ending up with overwhelmingly black colours. The evidence is taken from the annual purchases of high-grade luxury quality woollen textiles for the upper echelons of the civic governments of Bruges (from 1302 to 1496) and of Mechelen (1361-1415, and 1471 - 1550): for the burgermasters or mayors, the aldermen (schepenen), and the upper clerks. Thus, in the Mechelen civic accounts, 75 percent of the woollens purchased for these civic leaders, from 1471 to 1550, were black, uniformly dark black. In the first half of the sixteenth century, from 1501 to 1550, 98 percent of those woollens were black. While other colours – reds, greens, blues, browns – can also be found, they were purchased only for the lesser officials. Clearly the civic leaders, the urban ‘patriciate’ had acquired a decisive preference for black woollens, one also shown by the nobility. But at Bruges, in the four decades of the mid fourteenth century, from the 1340s (just before the Black Death) to the 1370s, the bright, vivid, red or scarlet, and multi-coloured textiles clearly predominated: varying from 72.4 to 81.7 percent by number purchased, and from 77.25 to 86.19 per cent by value. The differences in percentages by number and value is explained by the decisive prominence of the most costly and luxurious of all medieval woollens: the scarlets, dyed in the extremely costly brilliant red dye kermes (extracted from Mediterranean insects). Scarlets often accounted for over a third of the textiles so purchased in the 14th century, but their number fell sharply in the 15th century, along with the radical shift in the colour spectrum to much darker blue and then black textiles. This study explains the differences in the production costs and values of scarlets and of other dyed woollen broadcloths, while demonstrating with comparative price and wage analyses (i.e., the purchasing power of industrial wages) that only the very rich could afford to buy these textiles: that the principal markets were the nobility, the upper mercantile bourgeoisie, and political leaders. Indeed, a master mason would have to spend more than a year’s income to buy a scarlet. The famed Johan Huizinga (Autumn of the Middle Ages) had indeed commented on this predilection for dark and especially black (with purples) colours in the dress of the mid-fifteenth-century Burgundian court; but he was mistaken in his supposition that by the end of this century, clothing fashions had gone more toward blues, in light of the evidence from the Mechelen accounts. Huizinga and others have suggested various theories for this shift in the colour spectrum for textiles and for the later preference for the ‘dark side’, but none – including any that I can offer – is convincing. Economic historians, however, must not be so supply-side oriented that they ignore the vital question of colours and thus fashions in textiles, in creating market demand. For the subsequent victory of the New Draperies, over the costly, heavy-weight woollens of the Old Draperies, in producing lighter, cheaper, but also more brightly dyed textiles, in more vivid colours, a transformation followed by the massive influx of Asian printed calicoes (with radical floral and geometric designs), helped to create the market conditions for the 18th-century Industrial Revolution, in both geographic range and income distributions.