Chance led me from "pale" to "gray" through the Greek word "polios,* although I don't think Nabokov deliberately linked "Pale Fire" to the name of Shade's murderer, Gradus ( or James de Gray) -. but I thought this relation (if true) seems interesting.

Cf Line 17: And then the gradual; Line 29: gray

By an extraordinary coincidence (inherent perhaps in the contrapuntal nature of Shade’s art) our poet seems to name here (gradual, gray) a man, whom he was to see for one fatal moment three weeks later, but of whose existence at the time (July 2) he could not have known. Jakob Gradus called himself variously Jack Degree or Jacques de Grey, or James de Gray, and also appears in police records as Ravus, Ravenstone, and d’Argus. Having a morbid affection for the ruddy Russia of the Soviet era, he contended that the real origin of his name should be sought in the Russian word for grape, vinograd, to which a Latin suffix had adhered, making it Vinogradus

* pallor c.1400, from O.Fr. palor "paleness," from L. pallor, from pallere "be pale,"
related to pallus "dark-colored, dusky," from PIE base *pel- "dark-colored,
gray" (cf. Skt.palitah "gray," panduh "whitish, pale," Gk. pelios "livid,"
polios "gray," O.E. fealo "dull-colored, yellow,
brown").http://www.etymonline.com/index.php