The color blue is often associated with boys, while red (or pink) is associated with girls.
Neuroscientists Anya Hurlbert and Yazhu Ling demonstrated through a series of tests that women tend to prefer the red end of the spectrum. But is this a cultural phenomenon or is it biological? Chinese researchers demonstrated through another series of tests that this preference extends across cultures.
Hurlbert and Ling conjectured natural selection as a cause: Women were assigned the role of foraging for food and had to distinguish the red berries and fruit in the green brush.
Prior to 1910, red was the color deemed appropriate for boys and blue was the color for girls — the reverse. So why were these the colors associated with each gender, and why did they switch? And why at that time?
Notwithstanding the ubiquity of computer color-maps that can generate many shades of color, there are more words for the varieties of red in our language than blue. Primitive man would sit by a fire, and respect the red flame: its heat, intensity, and energy. Red was thus deemed a color that represented the traits needed for hunting and defending the tribe. So, perhaps that is why red became the color for boys — yes, perhaps color preference may be a cultural phenomenon, while based in physics. But could science be more involved in the switch?
In 1905 Albert Einstein began to publish his work. Scientists realized the nature of the red shift with regard to the Doppler effect on light waves. Blue light has a higher frequency than red light. Scientists discovered that blue stars are hotter than red ones. Blue is a more energetic color.
Around 1920 several family magazines began presenting pictures of baby boys dressed in blue-colored clothes. By 1925 the switch was in.
Is this a cause and effect? I don't know. But it makes an interesting conjecture. By the way, there is no evidence that Pablo Picasso ever met Einstein or was familiar with his work, when, around the same time, he shifted from his blue period to a red one. Still, one wonders about the intersections of science and art.