It’s easy to test whether you’re color blind. You don’t even need to go to a doctor. A set of images called the Ishihara color plates is one of the most common and reliable tests.

Simply look at the images, which have numbers embedded in dots of color. The numbers are a different color than the background. If you can’t see the numbers, you’re probably colorblind. School kids often take the Ishihara test as a classroom activity. It’s that easy. And can be fun.

But for anyone taking this test, it’s important to understand what it means to be color blind. The condition is uncommon and it’s rarely serious. Testing positive is no reason to panic.

The term itself is a little misleading. With rare exception, people who are color blind don’t live in a colorless world. They see most colors clearly.

Color blindness occurs when cone cells, located in the retinal tissue at the back of the eye, don’t function or are damaged. There are two main kinds of color blindness:

Red/green color blindness, the most common type, is congenital or inherited. It’s far more common in males than females, but still very rare. It affects 5 to 8 percent of males, and 0.5 percent of females. For people with red/green color blindness, reds and greens look similar to each other as a kind of brownish, muted tone. There is also a blue/yellow type of color blindness, but it's even more rare.

A second, and less common, kind of color blindness is acquired, or related to an eye disease or condition. Retinal or optic nerve disorders are most likely to cause this kind of color blindness. In these cases, symptoms such as overall failing vision or persistent dark or white spots may be noticed first. An ophthalmologist may test for color blindness to help diagnose the problem. The doctor may start with an Ishihara screening test and, if that’s positive, move to more sophisticated testing.