For nine days, the whole of Pamplona dissolves into a single color code. There's no legal requirement or access control demanding it, but white and red are, in practice, the uniform of San Fermín, and wearing it correctly is part of respecting the tradition.
What each color means
White — shirt and trousers — symbolizes purity and serves as the neutral canvas against which the second color stands out. Red — neckerchief and sash — represents passion and has a historical connection to the festival's bullfighting and religious tradition, evoking both the blood of the Running of the Bulls and devotion to the patron saint.
The key pieces
The pañuelico: the red neckerchief tied around the neck, traditionally not before the Chupinazo on July 6th. Many participants keep it from one year to the next as a personal memento, and some collect commemorative neckerchiefs from different editions.
The faja (sash): a red cloth band, usually around 2.5 metres long, wound several times around the waist. Originally practical — it used to protect the lower backs of farmhands working in the fields — today it's purely symbolic.
White shirt and trousers: there's no need for a specific brand; any simple white garment fulfils the tradition. Avoid semi-transparent whites if it's going to rain or you'll be sweating a lot, which is common in the middle of July.
Common tourist mistakes
Tying the neckerchief before the Chupinazo (which breaks tradition), wearing unsuitable footwear for walking and standing for many hours, and not protecting your skin from the sun because you think "it's just a night-time festival" — morning events, like the Running of the Bulls or the comparsa, take place in full July sun.
Is it compulsory to dress this way?
No, not at all. You can take part in the festival wearing whatever you like. But wearing white and red has a double advantage: you blend visually into the atmosphere and, above all, show a minimum of respect for a centuries-old tradition that the people of Pamplona themselves care for with great affection.