From A.A. Zimin ,"Vityaz na rasputie" ("Warrior at the
crossroads"), Moscow, 1990, kindly
suggested by Yury O. Chernoff: St. George the
Victor was originally a personal Coat of Arms of Yury (George)
Dmitriyevich, second survived son of Dmitry the Don, due to St. George
being his patron saint (O.S.: Russian name Yury originates from Scandinavian
variant of the name George - Goeran, spells [Yu:ran]). Irony of
history is in that for most of his life, Yury Dmitriyevich was a
Prince of Galich and Zvenigorod, not a Grand Duke of Moscow. He gained
Grand Duke of Moscow crown after a terrible war shortly before his
death at 1434, and was succeeded by his major rival, his nephew
Vassily the Blind. Strangely, Vassily inherited his rival's Coat of
Arms.
From Carl Alexander von Volborth's book on heraldry there's this picture about the coat of arms of Moscow :
"The rider is said to be St. George from 1730. This version of the arms is dated 1856"The dominant colors are in effect red, blue and white.
Another book says about the three colors:
"The imperial Russia had a red,blue and white flag, created in 1697 by Peter the Great, based on Holland's (...) It was the origin of pan-slavic colors, used by Serbia, Slovakia, Croatia and Bosna (...) The white-blue-red flag was used till the fall of Kerensky's government, in November 1917. The same happened to the two-headed eagle, without the imperial crown"Note that the 1856 version of St.George shows the rider going from right to left, while on modern shields bot rider and dragon are turned from left to right, whith the spear still in the foreground, making the right-handed knight's position more natural.
The Russian nationalists' black-yellow-white is based on
the Russian Emperor Standart of 1858-1917 which follows itself the colours of
imperial shield featuring black two-headed eagle on yellow field.
Aldo Ziggioto, the CISV (Centro Italiano Studi Vessillologici) president,
wrote a little book about the Russian flags: "Tre secoli di storia
attraverso le bandiere" (3 centuries of history thru flags).
According to him, both flags were drawn by Peter the Great:
"The military poop flag is white, with a full-sized blue cross of St.Andrew, because the Christianity became to Russian people from this apostle", explained Peter the Great in 1712. St. Andrew is also the patron saint of Russia. In fact since 1701 the Russian fleet was divided into 3 formations, each of them using a different flag: the first formation's (battle vessels) flag was white, the second one's (vanguard) was blue and the third one's (rear-guard) was red. All of them have a white canton with a blue St.Andrew cross.The Russian Navy used a very great number of flags, more than one hundred. The quoted book shows 22 of them.