Pasto’s major event is held on January 5 and 6. Its origins go back to the times of Spanish rule, when slaves were allowed to celebrate on January 5 and their masters showed approval by painting their faces black. On the following day, the slaves painted their faces white.
On these two days the city goes wild, with everybody painting or dusting one another with grease, chalk, talc, flour and any other available substance even vaguely black or white in tone. It's a serious affair – wear the worst clothes you have and buy an antifaz, a sort of mask to protect the face, widely sold for this occasion. Visitors with respiratory issues should not attend – you'll be coughing up talcum powder for days afterwards.