Mexico City ? A visitor here might be confused when suddenly, at the end of December, there appears in street stalls and market bins a mountain of underwear for sale. At subway stops, in grocery aisles, in department stores, it’s all about ladies’ undergarments, and always in the colors red or yellow.

The recently arrived might take a guess. A bitter sporting rivalry? The Red Devils against the Yellow Hornets?

Nope.

It is a popular New Year’s ritual for women in Mexico to don fresh briefs to ring out the old and ring in the new, and apparently nothing says Happy 2010 like a pair of bloomers — red for love and yellow for wealth (and no fair wearing both).

Because the choice of a color signifies one’s aspirations for the coming year, newspapers in Mexico send out reporters to quiz vendors about the national mood, and as 2009 — a year of soaring drug violence and deep economic tremors — shuddered to a stop, the vote was clear.

“Yellow. That’s all they want. I am selling twice as much yellow as red,” said Lucia Mendoza, making some last-minute sales on New Year’s Eve on the sidewalk outside the central market in the capital’s Coyoacan neighborhood.

Milenio News reported a go-go market for yellow. El Universal found yellow ahead by a mile. Makes sense. Mexico’s $1 trillion economy shrank by more than 7 percent in 2009, the hardest-hit in Latin America, a victim of the recession in the United States, Mexico’s No. 1 trading partner. Everybody here is ready for a jump-start in 2010.

The donning of red and yellow panties is a relatively new phenomenon in Mexico, which values its old holiday traditions but appears ready to try on another one.

New Year’s Eve is usually celebrated with a late dinner of turkey or cod at home with family and friends drinking punch and waiting for the fireworks. At the stroke of midnight, Mexicans gobble a dozen grapes, making a wish with each one.