Prior to the 1100s blue was seen as the colour of barbarianism, mourning and misfortune (feeling blue…got the blues etc)
However, once we hit 1400s blue, and ultramarine blue, which was so expensive, became the choice of colour for depicting the Virgin Mary. Blue gained in popularity with manufactured blue dyes and paints, and dark blue now suggests authority, a trustworthy and respectable person, (particularly after the war with the blue used in uniforms). Blue became the choice for baby boys, a complete change around from blue being seen as delicate. In the 1900s most children just wore white linen dresses.