Circle all the red apples and cross out all the green apples. This type of Kindergarten assignment seems benign, but for some children with color blindness, it is actually impossible. 

Color blindness, or color deficiency, means being unable to differentiate between certain colors, most often green and red, sometimes blue and yellow.

The genetic condition is much more common among boys, and about eight percent to nine percent of U.S. males are color blind. In children, red-green color blindness is by far the most common and is usually very mild.

There aren’t a whole lot of cues to make parents aware there’s a problem, so the condition is usually discovered in school. “Kids just can’t tell the difference (between colors), and that will prompt the parents to come in and get it checked,” says Dr. Adam C. Martin, OD, optometrist at the Baton Rouge Clinic. There are also school screenings that can check for color blindness.

The typical screening uses the Ishihara test for color deficiency, developed more than 100 years ago. The 14 plates feature shapes made out of dots, such as a number, letter or squiggly line. Being unable to see the shape would indicate color blindness.

“There’s not a whole lot we can do for it anyway,” Dr. Martin says. “There’s not really anything that can help them see the color.” But there are accommodations that a child’s school or teacher can make to help them work around it.

Special glasses or contact lenses can help someone distinguish between colors, but there’s no way to see colors normally, Dr. Martin says. Apps can also provide that differentiation, which can be helpful for choosing clothes that match.

Our society makes other accommodations for color blindness, such as with traffic lights. Red is always on top, which is how drivers who can’t tell the difference between red and green know when to stop.

A few jobs require perfect color vision, such as pilots, crane operators and some military jobs, and most people with color blindness lead typical lives. “There’s not a whole lot where it’s going to hold them back in life,” Dr. Martin says.