Illustration by Zach LiebermanWhen I first read about olo, a never-before-experienced color that scientists had conjured in a lab at the University of California, Berkeley, I realized I didn’t really know what color was. Humans typically have three types of retinal cone cells, termed L, M, and S. In natural seeing, it’s always some mix of those three types that is stimulated. In my reporting for a story in this week’s issue, I spoke with the olo scientists and with other color experts, including my friend Julian Kreimer, an artist who has taught courses on color for many years. Only seven people have ever seen olo. I came to learn that experiencing a color, any color, is far more complicated than engaging a pattern of cone-cell stimulation, and that olo, in addition to being a previously unseen color, was also a clue to the still mysterious details of how we see color itself.