Looking for new colors?

Science has uncovered a new color. No, we’re not talking about a new shade with a name like “violet indulgence” or “likeable sand” in the hardware store paint aisle; it’s a color that has never been seen with human eyes. It’s called “olo” and has been described as an intensely saturated blue-green. Researchers at UC Berkeley, leaning into the fantastical spirit of this endeavor, developed a technique named “Oz” to uncover the new hue. But no wizards or witches were needed in this endeavor - just science.

At a basic level, color is light. All light carries energy, which is measured by its wavelength. Colors each have a unique wavelength within the visible spectrum (the range detectable by human eyes, typically between 380 and 700 nanometers). Our perception of color begins with specialized cells in the eye called rods and cones. Cones are responsible for processing color, where rods are responsible for handling white, black, and grey signals. These cells detect color through “photoreceptors” on their surface, which are like little TV antennas that pick up light. Once these cells receive the ‘signal’, they then send it to the brain for further processing through nerves in the eye.

There are three different types of cones within the human eye, each named for the type of wavelengths it detects. S cones (short wavelengths) pick up blue light signals, M cones (medium wavelengths) detect green light, and L cones (long wavelengths) recognize red light. There are a few theories on how we see the full spectrum of colors using just these three cone types, but they all involve a combination of the cone cells working together to create different hues. The idea is similar to how a RGB color mixer on a computer works – combining certain proportions of red, blue, and green will lead to any color. We are constantly taking in multiple wavelengths of light, so we always have combinations of cone cells being activated at one time. But is it possible to only activate one specific type? What would the outcome on color perception be? These are the questions asked by the research team that discovered olo. 

Ren Ng and his team of researchers developed their technique, Oz, to target specific populations of cone cells within the eye. To begin this process, they had to characterize the cone cells in each study participants’ eyes. They did so by using adaptive optics scanning light ophthalmoscopy (AOSLO), a technology used to scan retinas and characterize the cells within, essentially creating a map of the eye. Using “coordinates” on these maps, the researchers pointed lasers with varying wavelengths of light at precise locations within the participants’ eyes to activate specific cells. Participants were asked to describe the colors or patterns they saw. In pilot experiments, they used known combinations of light to activate corresponding arrangements of cone cells and simulate typical colors. Once they achieved this, they moved on to activate only the M cones within the eyes, which led to the perception of olo. This color is described as a rich teal color of “unprecedented saturation,” which aligns with the middle wavelengths that M cones detect. Moreover, researchers had to add in white light and ‘wash out’ olo in order for participants to identify the resulting color as something they’d seen before. This confirms the specific activation of M cones within the eye and the perception of a novel color by human beings. 

While the discovery of a new color is baffling and exciting on its own, this research can also increase our understanding of vision and color perception. The Oz technique will continue to be refined and expanded – Ng and his team have already used it to trick participants’ brains into seeing a full color video. Oz also paves the way for other inquiries into how our eyes detect color. For example, people who experience colorblindness have missing or defective cone cells in their eyes. If a technique such as Oz can simulate perception of new color, it may also help colorblind individuals see colors they would not have before. 

On a more philosophical note, the discovery of a new color sparks discussion about perception and the world around us. People often take the common idiom, “you have to see it to believe it,” a little too seriously. We refuse to believe something unless we see hard evidence to support it with our own eyes. However, olo is an example of something that exists in the world that we did not have the capacity to perceive on our own. What other ‘olos’ are out in the world right now, waiting to be uncovered? We might not be able to see them or even imagine them, but that does not mean that they are not there. When we humble ourselves to this truth, it helps us create new ways toward discovery. There’s always something to be uncovered; we just need to take new approaches to find it.