> The most interesting thing for me is that while cyan (#00ffff) is nominally halfway between blue and green, most people's thresholds, averaged over monitor calibrations, imply that cyan is classified as blue.
Perceptually (that is, in CIE-LCh color space, for example), the hue component of #00ffff is a lot cloer to #00ff00 than it is to #0000ff. But the website doesn't ask which color is closer, it asks if it's "green" or "blue". And how we use those words has more to do with culture than with perception. We also call the color of a clear afternoon sky "blue", even though that is perceptually extremely far away from #0000ff.
Perceptually (that is, in CIE-LCh color space, for example), the hue component of #00ffff is a lot cloer to #00ff00 than it is to #0000ff. But the website doesn't ask which color is closer, it asks if it's "green" or "blue". And how we use those words has more to do with culture than with perception. We also call the color of a clear afternoon sky "blue", even though that is perceptually extremely far away from #0000ff.