During the Roman Empire, yellow was a symbol of wealth because of one particularly pricey spice: saffron.
Saffron is the most expensive spice in the world, which is not surprising when you consider the fussy plant it comes from. The Saffron Crocus produces a fragile flower that blooms at dawn and wilts by the end of the day—requiring quick harvesting. An entire field will have flowering for only a few weeks in mid-autumn. The flowers are harvested by hand, and then have their red stigmas plucked while the rest of the flower is discarded. It's a delicate process that defies mechanization; currently there is no efficient way to use a machine in the production of Saffron—every piece has been carefully collected by human beings.
Eventually Roman emperors started to favour a particular purple dye (more about that interesting story can be found here) and Saffron Yellow fell to the wayside in the Roman fashion scene. With the decline of the Roman Empire, Saffron production in Europe died out, and people turned to alternative methods for creating yellow. However, during the middle ages, Europeans saw yellow as nothing better than a sullied white (they preferred gold for that "sunshine" feel). Yellow was the devil's colour; the colour of jaundiced skin, bile, and sulphur; the colour of sinners, non-Christians, heretics, fallen women, assassins, and traitors. Medieval paintings of Judas usually featured the betrayer of Jesus in a yellow robe. Some Italian communities even had rules that required Muslims and Jews to identify themselves as non-Christians by wearing something yellow.
It was not until the Moors started expanding north from Africa and into southern Europe that Saffron was reintroduced into Europe (Spain is still known today for its particular type of Saffron). It was used less for a clothing dye and more as a food colorant, spice (obviously), and as a cheap alternative to Gold Leaf for illuminated manuscripts. Europeans started growing the crocuses and harvesting the Saffron using free labour. Many European towns had initial years of great wealth and success, followed by years of low crop yields that resulted in communities abandoning the crop. By the 1250s, Pilgrims and merchants from the Middle East helped bring Crocus into France. 100 years later, the Plague devastated Europe. Saffron, a popular remedy for the plague at the time, was in huge demand. The problem? Many European Saffron farmers were now dead or ill and Crusade-related animosity made importing it from the Middle East difficult (considering conflicts in the Middle East today, it is interesting to note that 90% of Saffron comes from Iran). Prices skyrocketed. Many Mediterranean Islands started growing it to get a foot in the business. Saffron became such a important spice that it even started a war.
The Saffron War of 1374 lasted 14 weeks and was a struggle between the nobles and merchants in Medieval Switzerland. The nobles were trying to claim land and power from the commoners as they felt they had the aristocratic right to do, and the merchants, unsurprisingly, did not feel so inclined to allow them. Arguments ensued and the merchants retaliated by sabotaging the nobles' hunt and attacking them in the woods. The nobles responded by hijacking the merchant's 800 lbs of Saffron (worth + $500,000 on today's market) that had arrived fresh from Greece. They held the Saffron hostage in a castle until it was eventually returned to the merchants. Saffron piracy was a big deal however—many Mediterranean ships were specifically attacked because of the lucrative Saffron onboard.
Saffron never really became popular again as a dye or a paint (other, less expensive yellows could be used that looked just as good and lasted longer) but yellow itself eventually left behind its association with sin. Renaissance artists started taking up the colour as it not only gave a more realistic hue to caucasian skin, but it also made gold items in a painting look more realistically gold than actual gold paint did.
Today, yellow is the colour of warmth and optimism, sunshine and joy, energy and goodness. Despite these glowing attributes, it is rarely chosen as a favourite colour. It may not be as flashy as red or as popular as blue, but it's powerful with black and white photography, makes purple pop, and deserves a little more love. You do you, yellow.
Thank you to Jaime for suggesting the colour yellow for this post. What colour should I do next?
All About Colour by Janice Lindsay
Color: A Natural History of the Palette by Victoria Finlay
Secrets of Saffron: The Vagabond Life of the World's Most Seductive Spice by Pat Willard