If you're a man and you may hate fruitcake, you may have a better reason than most. For an estimated 8 percent of the male population, the red-and-green dotted holiday treat is visible only as a greenish brown mass. These men--one out of every 12--have red-green color blindness. meaning only blues and yellows are visible as vivid shades, while reds and greens appear brownish and murky.

"Red-green color vision defects are not that rare," says Arthur Bradley, a professor of optometry at Indiana University. "The term 'color blindness' is used to describe limited color vision, usually with respect to reds and greens. Blue-yellow vision is very rarely affected."

While bright red and green holiday decorations appear monochromatic to people with limited color vision, the Jewish winter festivities don't change greatly in their eyes. Hanukkah decorations often incorporate blue and white, the colors of Israel, and gold colors may be present in the menorah and other traditional motifs. These blues and yellows look much the same to people with red-green color vision defects as they do to those with normal vision, but holly, red and green Kwanzaa candles, and yes, fruitcakes, all appear to be shades of brown.

Gazing at decorations may not present a practical challenge but preparing the holiday meal is undoubtedly more difficult for people who cannot distinguish reds and greens. For example, "judging when meat is cooked is a challenge for people with color vision defects," Bradley says. "Determining the ripeness of fruit and vegetables is another problem." Selecting an outfit, interpreting traffic signals, and following sports on television are other color-vision challenges, he adds.

Although color blindness is common among men, very few women have the condition. "There are several different types of color blindness, but nearly all are much more common in males, because the genes coding the condition are recessive on the X chromosome," says Bradley. "Men have only one X chromosome and women have two, so if a man inherits the gene he will be color blind, but a woman will not unless she inherits it from both parents."

Upload your own photos to http://www.vischeck.com to see how they appear to someone with a color vision defect.