The precise triggers for anthocyanin production could thus take years to figure out.

ECONOMIST: The science of autumn

Where these signals intersect, the production of red anthocyanin pigments is induced.

BBC: A bumblebee extracting nectar and pollen from a snapdragon

But the reason for youthful blushing which, like the ruddiness of old age, is due to the presence of anthocyanin pigments need not be the same.

ECONOMIST: Young leaves, as well as old ones, are often coloured red