In Colombia, yellow underwear is traditionally worn on New Year's Eve to attract good fortune.
The custom is part of a broader set of New Year's rituals found across Latin America, where colors and objects are assigned hopes for the coming year. Yellow is commonly linked with luck, prosperity, and positive energy in Colombia's New Year's traditions.
Some people wear the garment inside out before midnight and turn it right-side out afterward, while others put it on at midnight. Practices vary by family and region, so the timing is not as universal as the yellow color itself.
Red underwear is often associated with love or romance in other countries, which can cause confusion. In the Colombian custom described here, the conventional color connected with luck is yellow.