I don't think the idea of the russian court dress was to be 'trend setting'. It was introduced in the 1834 by Tsar Nicholas I to enhance the "Russian" or national characteristics of the dress worn at court and to distinguish the Russian court from the other European courts. I think it did that very well. The "armour" the ladies wore was very distinctive and even now makes it easy to see that it the Russian court the wearer comes from or is attending. You are correct about the colour ranks in the dress.
these are some notes I have on the dress style from various online sources:
"In 1834 Nicholas I written an ukaze about the court dress:
maiden of honnor to the Empress: red velvet embroided in golden (unmarried women)
ladies in waiting to the State: green velvet embroided in golden (married women)
ladies in witing to the grand duchesses : blue velvet embroidered in silver
The Empresses wore cloth of silver or cloth of gold (according to her preference) for high state occasions, or colored silk embridered with gold or silver for lesser state occasions. The Empress' favorite color was reserved for her personal use; Alexandra's was an intense rose pink, Marie's a deep cerise.
Each Grand-Duchess also had a color reserved for her exclusive use; Xenia's was peacock blue, Maria Pavlovna the elder's was a siennese orange, Grand duchess Elizabeth was aquamarine etc.
The costumes of the attendant ladies in waiting were as follows; The ladies-in-waiting to the Empresses wore
red velvet embroidered with gold. Ladies in waiting to the grand duchesses wore forest green velvet enbroidered in gold. The unmarried ladies in waiting had picturesque capes which covered their bare shoulders. Married ladies were required to attach long tulle veils to their kokoshniki (headdresses).
ladies-in-wating to the empresses (in red) were always unmarried, and they were called "Freliny" (From the german word, Fraulein).
Maids of Honour who attended the Empress: Same cut and design dress as above, but dress made of crimson velvet embroidered with gold.
Maids of Honour who attended Grand Duchesses (wives of Grand Dukes): Same as above made of crimson velvet embroidered with silver.
Maids of Honour who atteded Grand Duchess (Daughter or Grandaughter of Emperor): Same dress design and cut as those above, but made of light blue velvet.
After marriage, these girls became "Dames d'Honneur" and switched to the dark Green Robes.
All of these women wore a "Chiffre" on the left shoulder, which was the diamond monogram of the member of the Imperial family whom they served, which was suspended from the Ribbon of the Order of Saint Andrew. If they were in service for many years, they were additionally offered the "Damy portret" which was a miniature of the Empress surrounded in Diamonds, and suspended from a ribbon. There were a finite number of these "Damy Portrety" (I believe only 20) and it was a coveted honor; when a woman retured, her position would be offered to the next woman to be honored. There were a few women who served multiple empresses, and some who had served first Marie, and then Alexandra who wore double portraits.
The portrait was not automatically bestowed with the position of "Dama" but was acquired later.
I have also read of the "violet" train of the Freliny, but of the dozens of uniforms I have seen in the collections of the Catherine Palace, Pavlovsk, THe State Russian Museum, and the Metropolitan Museum here in New York, I have never encountered a violet (which I take to mean purple) train.
The length of the train was determined by the rank of the wearer, the longest belonging to the Empresses, (as long as three metres) followed by Imperial Grand Duchesses (by birth), Imperial Grand Duchesses (By marriage), Imperial Princesses of the Blood (by Birth) Imperial Princesses of the Blood (by Marriage), Princesses of the Old Nobility (by Birth. then by Marriage) Countesses, Baronesses, etc. Position at court could increase the length of the train, as could the position of one's husband!
The Empresses' trains were carried by four (six?) members of the Corps des Pages (who wore gold-embroided short black frock coats over white doeskin trousers (which needed to be slid on after spreading talcum powder over the thighs, and which were then sprayed with water so that they would contract and fit snugly) and knee-high black patent leather boots. The grand duchesses trains were carried by their ladies-in-waiting.
Women who attended court functions (women who were without position at court) were required to wear dresses cut in the same style -- but the color, type of fabric, length of train and amount of embroidery was very much restricted. "