Thanks Skuzzy. They're from the 2000 Library of Congress digital scan.
"The Library of Congress undertook a project in 2000 to make digital scans of all the photographic material received from Prokudin-Gorsky's heirs and contracted with the photographer Walter Frankhauser to combine the monochrome negatives into color images.[31] He created 122 color renderings using a method he called digichromatography and commented that each image took him around six to seven hours to align, clean and color-correct.[32] In 2001, the Library of Congress produced an exhibition from these, The Empire That Was Russia: The Prokudin-Gorskii Photographic Record Recreated.[33] The photographs have since been the subject of many other exhibitions in the area where Prokudin-Gorsky took his photos."