Koriathain don't wear 'uniforms' - but there will be symbolic or direct tags on their garb to designate rank and position.
Lirenda is a clothes horse, definitely!!! She comes from an aristocratic background and absolutely liked 'fancy' and 'rich' - repeatedly she is described as obsessed with impeccable grooming.
The Koriathain 'colors' are, yes, deep purple, lavender, silver or silver gray, and red.
The jewels they wear follow suit:
amethyst, moonstone (both are quartz based/could be active focuses), garnet for low rank, ruby for high, pearls and diamonds.
The silver ribbons of charitable service would be on the sleeves, likely - though a cloak hood or hem might bear that tag, also. They would be silver gray satin, not metallic trim (that would tarnish and these are the lower echelons of the order). So low rank would be silver ribbons, likely on dove gray wool or linen. There are THREE ranks in this echelon - one ribbon for initiate rank, up to three for the depth of talent and knowledge. There would be MANY powerful enchantresses of third rank, in this echelon - ones who were gifted healers or seers, but who were not considered worthy (for reasons of character) of administrative rank.
Administrative rank is denoted by SCARLET BANDS and there are six ranks (above the basic 3 of charitable service). Enchantresses in this echelon are privy to some if not many of the secret intents - they are the ones who carry out orders with some degree of awareness. Not all enchantresses would fit here - (Elaira, for one, would be too outspoken and too honest to handle the layers of intrigue) - Koriathain DO believe the means justifies the end - and the ones who have too much conscience would never rise to these positions.
So you would have scarlet bands of rank UP TO NINE - ONLY the Prime would wear nine!!! Lirenda, as First Enchantress, was the ONLY one in the order to hold Eighth Rank.
An enchantress 'graduating' from third rank charitable to 'fourth rank' administrative - would be four bands. She crosses into the ranks of the decision makers and her silver ribbons change color.
The sleeve designs, bodices, girdles - shoes - all vary according to environment. Outdoors, or riding, think practical. INdoors - could be very ornate for show OR practical - depending.
The banner of the Koriathan has a swan - so - jewelry or embroidery may carry that emblem in the design.
You might find seed pearls or embroidered jewels in the very ornate costumes.
If Lirenda was listed as wearing 'gold or silver trim' on her clothing, this would have been preferential - ornamental - and not indicative of rank.
Personal crystals: would be clear quartz. They could be natural points, or polished, or faceted, or even, spherical. If they were cut, they would have been 'energetically' enhanced or at least, cut in line with the original crystal's natural axis so that the flow was not disrupted.
Anything labeled as a purse would be a drawstring bag or a belt, practical in design, and used in place of pockets, which would not be as 'secure' for carrying arcane items or crystals.
Hair for Koriathain could be worn netted, braided, or pinned up - not likely to be loose.