In a comment a while back, Elena pointed out that Diego Velázquez’s painting “Infante Felipe Próspero” (from 1659) provides a good example of how pink was acceptable for males to wear…as were, in some cases, dresses, which the young prince is wearing:

Elena says,

…until the late 1700s little boys would wear dresses or petticoats for as long as they could until they could dress as miniature adults…This was mainly for ease of bodily functions.

Of course, today most parents would be appalled at the idea of dressing toddler boys in dresses–dresses with frills and ribbons, at that.

The painting “Pope Innocent X,” also by Velázquez (1650) shows the Pope in light pink clothing:

Both images found at the National Gallery’s Velázquez page.

You might also check out Kent State University Museum’s Centuries of Childhood exhibit for examples of how children’s clothing has changed over time.

Thanks for the tip, Elena!