Seeing red? Feeling yellow with fear or green with jealousy? Those common expressions just go to show how tightly coupled color is in our lives.

Whether it’s in websites, printed material, or even the color of the walls, color can have a profound impact on our mood, emotions, physical reactions, and receptivity to marketing messages. “Red is the color of passion, but did you know that shades of red can entice hunger?” according to The Sequitur. “Next time you are out and about, count how many of your favorite restaurants include RED in their motif or logo in some way.” Similarly, some companies are using more greens to make their products look more eco-friendly, writes Talia Wolf in The Next Web. Organizations such as NASA have sets of guidelines on how best to use color for their employees.

Not everyone can see all colors, of course. Some people can’t necessarily see as many color gradations as others—stereotypically, a sex difference. “Neuroscientists have discovered that women are better at distinguishing among subtle distinctions in color, while men appear more sensitive to objects moving across their field of vision,” writes Libby Copeland in Smithsonian. “Women proved slightly better at discriminating among subtle gradations in the middle of the color spectrum, where yellow and green reside. They detected tiny differences between yellows that looked the same to men. The researchers also found that men require a slightly longer wavelength to see the same hue as women; an object that women experience as orange will look slightly more yellowish to men, while green will look more blue-green to men.”

More severely, there’s color blindness—also more prevalent in men—where people can’t really detect a difference between two colors (typically red and green). “For those with color blindness, living with it is, for the most part, not a problem,” writes Josh Haugen, who more properly describes himself as “color deficient.” “We have had it our entire lives and don’t know it any differently. It’s just how colors look (or don’t look) to us.”

Even separate cultures can perceive colors differently. “Before the modern period, Japanese had just one word, Ao, for both blue and green,” writes Aatish Bhatia in Wired. “The wall that divides these colors hadn’t been erected as yet.” Other Asian languages have a similar issue, as well as different ways of describing colors. But Japanese has gradually added the notion of “green.” “As the language evolved, in the Heian period around the year 1000, something interesting happened. A new word popped into being–midori–and it described a sort of greenish end of blue,” he writes.

But what really made the difference was crayons, Bhatia writes. “In 1917, the first crayons were imported into Japan, and they brought with them a way of dividing a seamless visual spread into neat, discrete chunks,” he writes. “There were different crayons for green (midori) and blue (ao), and children started to adopt these names.” In fact, cultures and languages tend to develop the concepts of particular colors in the same order, he adds, and having a separate name for a color—as with the crayons—may make it easier for people to perceive it.

On the other hand, some people’s worlds are even more colorful, such as by being able to see colors in sound or in numbers. “Such individuals have a neurological condition called ‘sound-to-color synesthesia,’ or ‘chromesthesia,’ in which they effortlessly and spontaneously experience their own personal light show while hearing music and other sounds,” writes Stephen Palmer in Nautilus. “Interestingly, many chromesthetes grow up assuming that everyone has the same visual responses to sounds as they do, and are shocked when they discover this is not so!”

Cultural differences in color can affect their meanings as well—which is significant if you’re designing something in color, whether it’s a website or a product, for an international audience. “We are not all primed to believe that red means ‘passion,’ blue means ‘trust,’ or green means ‘earth,’” writes John Giordano in Internet Retailer. “Depending on where you go, yellow does not always mean ‘cheerfulness,’ orange does not always mean ‘energy,’ and purple does not always connote ‘luxury.’” In particular, companies that have failed to pay attention to what color represents “death” in a particular culture have mismanaged many international marketing campaigns, he writes.

In the same way that some cultures have fewer types of colors, our modern culture has lost the ability to represent some colors. For example, it’s been said (correctly or not) that we have lost medieval artisans’ techniques for making particular colors, such as “Chartres blue,” after the stained glass color in the French cathedral.

That’s why Harvard University’s Forbes Pigment Collection is storing samples of more than 2,500 samples of various pigments. The collection helps art curators determine whether a particular piece of art is genuine, based on whether the colors used in it were available at the time it was allegedly produced.

“For example, their work was instrumental in proving that a Jackson Pollock painting ‘rediscovered’ in 2007 was actually a fake, after pigment analysis revealed that a specific red color was manufactured 20 years after the artist’s death,” writes Diana Budds in FastCo Design. “The color, Red 254, was a by-product of a chemical reaction first documented in 1974; it’s also nicknamed “Ferrari red.’”

In addition, the collection helps people keep track of colors that are not as common, perhaps because the pigment that produces them is toxic, or perhaps—as in the case of one particular kind of brown—it’s no longer acceptable to grind up mummies to produce it, even if it means the world no longer understands the notion of “Mummy brown.”

Obviously, without color, we’d all be feeling blue.