The fall of Failing Light (formerly known as Visionary Despina, the time-traveller, not to be confused with the Despina of our timeline) started a movement later known as the Masking. The nature of the movement is described as religious, political and artistic all at once - unsurprising considering that in Eunomia, faith permeates all things.

It is commonly agreed that the Masking was initiated by the Cultists of Fluidity. What is unknown is if it was organised by Failing Light herself before her death, or if it was somehow a spontaneous reaction to Failing Light's death.

Political People that took part in the Masking would don masks in public, at all times. They would wear different coloured masks to signal one's (sometimes self-proclaimed) caste identity: gold for Visionary, black for Champion, red for Realizer and iridescent for Potential. What is more revolutionary than the suggestion that one should be allowed to change one's role with even more fluidity is the call for additional castes, or the combining of castes. Later on in the Masking, many members of the movement started wearing masks of multiple colours, for example, gold and red for Visionary-Realizer, black and red for Champion-Realizer, etc.. Only allowed in Iridescent Provinces. If you're not in one you are strongly encouraged to go there.

Spiritual significance “Mask to unmask.”

“By donning the mask externally, we learn to unmask internally.”

Artistic Masks grew to be more and more elaborate and it in fact started to become fashionable. Maybe in a hundred years it will make it into their formal wear. Who knows with the Eunomians.