Sergei Prokudin-Gorskii / Library of Congress.
The only known color photo of Russian author Leo Tolstoy, circa 1908, in number 5 in Newsweek's Flash slideshow. The selections come from The Empire That Was Russia: The Prokudin-Gorskii Photographic Record Recreated (A Library of Congress Exhibition).

Prokudin-Gorskii's Color Photos of Russia, 1907-1915 leads to Newsweek's story and (unlinkable) Flash slideshow of 28 of the 2,067 photos whose glass plates ended up in the Library of Congress but were unprintable. The photographer, seen below, shot with RGB filters that digital technology can now render.

Self portrait by the photographer, Sergei Prokudin-Gorskii

About the Prokudin-Gorskii Collection at LOC:

The Sergei Mikhailovich Prokudin-Gorskii Collection features color photographic surveys of the vast Russian Empire made between ca. 1905 and 1915. Frequent subjects among the 2,607 distinct images include people, religious architecture, historic sites, industry and agriculture, public works construction, scenes along water and railway transportation routes, and views of villages and cities. An active photographer and scientist, Prokudin-Gorskii (1863-1944) undertook most of his ambitious color documentary project from 1909 to 1915. The Library of Congress purchased the collection from the photographer's sons in 1948.

(The keyword search is excellent, and can be filtered by subject and other ways.)

An Explanation of the Color Rendering Process, "Digichromatography" at the Library of Congress.

We know that Prokudin-Gorskii intended his photographic images to be viewed in color because he developed an ingenious photographic technique in order for these images to be captured in black and white on glass plate negatives, using red, green and blue filters. He then presented these images in color in slide lectures using a light-projection system [right] involving the same three filters.

Great stuff, technically and historically. Go there...

Thanks to my colleague Tim Barmann for this tip.