A new color, “olo” was observed for the first time.

The Scientific American:

What, exactly, did olo look like? Ng describes it as “blue-green with unprecedented saturation”—a perception the human brain conjured up in response to a signal it had never before received from the eye. The closest thing to olo that can be displayed on a computer screen is teal, or the color represented by the hexadecimal code #00ffcc, Ng says. If you want to try envisioning olo, take that teal as the starting point: Imagine that you are adjusting the latter on a computer. You keep the hue itself steady but gradually increase the saturation. At some point, you reach a limit of what your screen can show you. You keep increasing the saturation past what you can find in the natural world until you reach the limit of saturation perceptible by humans—resulting in what you’d see from a laser pointer that emitted almost entirely teal light. Olo lies even further than that.

To check if what the participants saw as olo really was a color beyond humans’ standard visual range, the researchers completed color-matching experiments in which they could compare olo with a teal laser and adjust the color’s saturation by adding or subtracting white light. All participants found that if they added white light to olo, desaturating it, the new color would match the laser, confirming that olo lies beyond the normal human range of color vision.

I know another “color” that lies beyond the normal human range of color vision...Sky Blue for the MacBook Air.