Once upon a time I was seduced by the sheer monumental scale of these mophead hydrangeas on an estate in Portugal. I think I liked them also for their combination of blue and green, my two favorite colors. I read today that both humans and animals are most sensitive to the blue-green region of the visible spectrum. Before the depletion of the ozone layer, most radiation entering the Earth's atmosphere was in the blue-green range, ie, 500 milicrons. Incidentally, it is this range of the spectrum that is most conducive to life. I have always had a preference for the colors blue and green best because to me, they are the colors of what I see and love most in nature–plants, sky, and water. I didn't realize that there was a scientific explanation for my predilection.