What are the symbolic meanings of colors in Freemasonry?

Blue is the primary symbolic color of the Craft degrees 1. It represents universal friendship and benevolence, taking its meaning from the celestial vault of heaven, which covers the entire globe and reminds Masons that these virtues should be equally broad in the breast of every brother 1. Consequently, blue and white are the only colors appropriate for decorating a Master's Lodge 1. White itself carries the long-established symbolism of purity and innocence 1.

Yellow plays a very minor role in Craft symbolism 1. Its chief appearance in early Craft tradition occurs in eighteenth-century ritual catechisms, where a "yellow jacket and blue pair of breeches" served as an emblem representing the compasses—the yellow jacket signifying the brass body and the blue breeches the steel points 1.

Purple is not a symbolic color belonging to the three degrees themselves, but it appears within the governance of the Craft 1. In English Freemasonry, Grand Officers and Provincial Grand Officers wear purple collars and aprons—giving rise to the term "purple brethren"—drawing on the ancient tradition of purple as an emblem of exalted office and supreme authority 1.