There is a fairly involved definition of "basic color word" that goes into this research. Basically, most English speakers would agree that periwinkle is a shad

There is a fairly involved definition of "basic color word" that goes into this research. Basically, most English speakers would agree that periwinkle is a shade of purple, but would certainly not say that green is a shade of blue. In this sense purple, green, and blue are basic color words but periwinkle is not.