Justin works in his reading workbook. The directions say to draw lines to the red balls. Too bad all the balls look green to Justin. He guesses and gets many of them wrong.

Haley's teacher writes the vocabulary words in orange on a green chalkboard. Haley can't distinguish most of the letters against the background. Embarrassed, she doesn't copy the words and gets an F on the vocabulary test.

Andy usually loves to read aloud in class. Today, however he balks when the teacher calls on him and claims he can't read. The story in the reader is printed in purple with a blue background.

For these kids, red, orange, yellow and green are simply different names for the same color. Approximately 10 percent of boys are colorblind, while only half of 1 percent of girls lack full color vision. This genetic deficiency usually passes from mother to son in alternate generations. You might think someone who is colorblind only sees in black or white — like watching an old black-and-white movie on TV. But that's not true. It's extremely rare to be completely colorblind. Most kids who are colorblind can see color. They just don't see the same colors as the rest of us.

Two types of cells in the eye detect light — the cones and the rods. Cones are responsible for our color vision. They are sensitive to red, green and blue wavelength light. "Colorblind kids lack some of one, two or all three of these cones," says Scott Steidl, M.D., director of the vitreoretinal service at the University of Maryland School of Medicine. Those who see every color of the rainbow can distinguish between more than 100 hues. But colorblind kids deal with a different palette. Most see only a handful of colors, and some see less than that.

Because colorblindness is a social inconvenience, parents and teachers should be especially aware of kids with the deficiency. "Colors are used as tools of communication to teach reading and math," says Steidl. Books and worksheets come in a rainbow of colors. Counting beads, chalk, maps and other activities all include color. There's no way that kids who can't see the material will be able to learn it. Children who are colorblind are easily misdiagnosed with learning disabilities, inattentiveness or laziness in school.