If a friend asked you to hand her a blue item from the rack above, you likely wouldn’t know which one to reach for. If she specified that she wanted the indigo blouse, you still might not know which item she had in mind.

Even knowing that indigo appears between blue and violet on a rainbow, you and I might not pick the same blouse because we likely have different ideas of what indigo is.

What is color?

Color is one of the most widely misunderstood visual principles, according to Virginia Commonwealth University researchers who have developed software that analyzes an image to identify all of its colors.

"This misunderstanding stems from the fact that the vast majority of people believe color is a physical property of an object rather then the perception and interpretation of visible wavelengths that emanate from or are allowed to pass through an object that has been affected by luminance," the researchers' website, MappingColor.com, reads.

However, our eyes are actually not that great at perceiving color. They mainly evolved to see spatial relationships, which makes sense as it was more important to figure out how far away a predator was rather than what color its fur was.

Robert Meganck, chair of the Department of Communication Arts at VCU, says another part of the problem is how we learn about colors from an early age.

"When you were in kindergarten, your teacher held up a crayon and said, 'This is red.' What you saw, you associated with the word red," he told VCU News. "What the person next to you saw, they associated with the word red, but you did not necessarily see and register the same color."

Why? Because we're often taught to identify colors without gaining a full understanding of color wavelengths, intensities and saturations.

So we can easily identify colors as being various shades of red, but we may have different ideas about what constitutes crimson or scarlet, or at what point red becomes orange.

Also, our ideas about color are deeply integrated with our other senses, as well as our experiences. It's why people can eat different colors of M&Ms and perceive a variety of tastes even though all the candies are chocolate.

"You don't know that you're seeing differently than somebody else, but in reality, in all probability, that's what you're doing," Meganck said.

colorful eye

Photo: PeterPhoto123/Shutterstock

Different realities

You've likely had some recent experience with this. Remember the dress? To some people, it's white-and-gold, but to others, it's black-and-blue, proving that we can look at the same thing and see it differently.

It's not a new concept.

About 8 percent of men and 0.4 percent of women have some form of color blindness, and though it's even more rare, there are even people with monochromacy, meaning they see the world and black and white.

Tetrochromats, on the other hand, are able to see about 99 million more colors than the average person, so when they look at the blue clothing above, they may see thousands of different hues. When tetrochromat Concetta Antico looks at the infamous dress, she sees numerous colors.

"It has hints of lilac, blues, grays, pinks... not bright but subtle... it is definitely not appearing dark as in black or dark blue on my monitor. In the gold area or lace there is some gold yellow but also grayish gold brown and lighter gold beiges."

Also, people with synesthesia may see this text in multiple colors other than black or even perceive the letters in this sentence as having personalities.

In other words, there are numerous examples of how different people can see the same thing differently without even realizing it, or as neuroscientist David Eagleman puts it, "We all accept the reality presented to us."

melted crayons

Photo: i-m-a-g-e/Shutterstock

Another name for 'blue'

Because we all perceive and experience color differently, we're limited in how we can talk about color and even how we use it.

But Meganck and his colleagues at VCU are hoping to change that with Color Gamut, software that creates a 3-D color map by analyzing each pixel in an image and plotting colors using three parameters: hue, chroma and value.

Hue defines the wavelength of the color, chroma is the degree of saturation, and value is expressed as a percentage to specify how light or dark the color is.

So instead of assigning a color a name like "blue," it's given three numerical values.

Although it may seem strange to think of color in terms of numbers, the Color Gamut actually gives names to previously unnamed colors. Or, as Meganck would say, it gives us more crayons.

"Identifying color in an everyday sense is like having a finite number of crayons. The more crayons you have, the bigger your gamut is — the more colors you can identify," he said.

While such software has obvious benefits within the art world — such as teaching color theory and determining the deterioration rate of artwork — it also has many other uses.

Color Gamut could be used by medical professionals to diagnose tumors or analyze blood simply by examining a sample's color data.

Scientists also hope to use the software to measure color changes in plants to detect buried explosives. Undetonated landmines leak chemicals into soil over time and can contaminate plants, causing subtle changes in their color that can be overlooked by the human eye, but easily identified by a computer.

The VCU researchers plan to have a full beta of Color Gamut ready for use by researchers and the general public within the next year, and they hope more practical applications are found for the software.

"It's almost overwhelming when you begin to realize that 'color' is a vital part of almost everything," VCU communication arts professor Matt Wallin said.

How well do you see color? Take the Color Challenge and find out.

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Laura Moss writes about a variety of topics with a focus on animals, science, language and culture. But she mostly writes about cats.

What's blue to you isn't blue to me
We perceive color differently, but new software that maps every hue may change the way we think about color.