I know that Vladm mentioned this book somewhere else in the forum, but I tried search and I can't find it.
This is a coffee table book printed in 1980. The complete title is Photographs for the Tsar - The pioneering color photography of Sergei Mikhailovich Prokudin - Gorskii commissioned by Tsar Nicholas II
The color photos are truly wonderful, however, over half of the book is still in sepia or black and white.
The are no photos of the Imperial Family except for a black and white of Alexi because Produdin-Gorskii may not have brought them out of Russia with him when he fled the revolution.
Quote from the introduction page xxii ( ) are mine.
"His collection of slides remained basically intact, although he was obligated to leave behind his projector and equipment. Certain pictures and negatives were deemed to have strategic value, and were confiscated by the authorities. These for the most part were the pictures taken to satisfy Rukhlov (S. V. Rukhlov Minister of Ways and Communications), and according to Prokudin-Gorskii they "had no meaning for the general public". In addition he left behind ten negatives of the Romanov royal family, about which he stated only that they were "hidden in Russia." To this day there is no evidence that they have been found."
I know that Vladm posted a link to a site where the pictures are posted on line, and that was what caused me to look into buying it. The color pictures are breathtaking and look as if there were taken just yesterday, not 100 years ago.