1951, proprietary name (Dane & Co. of London) for a brand of fluorescent paint. As an adjective, with reference to colors and patterns, by 1959.
U.S. state (organized as a territory 1861, admitted as a state 1876), named for the river, Spanish Rio Colorado, from colorado "ruddy, reddish," literally "colored," past participle of colorar "to color, dye, paint," from Latin colorare "to color, to get tanned," from color "color of the skin, color in general" (see color (n.)).
region in Luzerne County, Pennsylvania, from Munsee Delaware (Algonquian) chwewamink "at the big river flat," from /xw-/ "big" + /-e:wam-/ "river flat" + /-enk/ "place." Popularized by 1809 poem "Gertrude of Wyoming," set amid wars between Indians and American settlers, written by Scottish author Thomas Campbell (1777-1844), who seems to have had a vague or defective notion of Pennsylvania geography:
On Susquehanna's side, fair Wyoming!
Although the wild-flower on thy ruin'd wall,
And roofless homes, a sad remembrance bring,
Of what thy gentle people did befall;
Yet thou wert once the loveliest land of all
That see the Atlantic wave their morn restore.
Sweet land! may I thy lost delights recall,
And paint thy Gertrude in her bowers of yore,
Whose beauty was the love of Pennsylvania's shore!
et cetera. Subsequently applied 19c. to other locations (in Kansas, Ohio, and Wisconsin), and to a western territory organized July 25, 1868 (admitted as a state 1890).
On the same day there was debate in the Senate over the name for the new Territory. Territories often keep their names when they become States, so we may be glad that "Cheyenne," to be pronounced "Shy-en," was not adopted. "Lincoln" was rejected for an obvious and, no doubt, sound reason. Apparently, nobody had a better name to offer, though there must be plenty of Indian words that could properly be used, and, for the present, the insignificant "Wyoming" is retained. [The Nation, June 11, 1868]