As far back as the 1740s. Correspondance between colors and genders is quite old. Still, people were then more concerned with distinguishing children of both genders from adults than with distinguishing boys from girls. 

As far back as the 1640s. Correspondance between colors and genders is quite old. Nonetheless, people were still very concerned with distinguishing boys from girls but they did so with hair styles rather than the color of their clothing.

As recently as the 1840s. Before that there was no set correspondence between colors and genders. Nonetheless, people were still very concerned with distinguishing boys from girls but they did so with hair styles rather than the color of their clothing.

As recently as the 1940s. Before that there was no set correspondence between colors and genders. In fact people were more concerned with distinguishing children of both genders from adults than with distinguishing boys from girls.