The Origins of Wonder
Jack McMillen and Judson Brown contributed “Telltale Color” to The Sphinx, Vol. 33 No. 1, Mar. 1934, p. 12. In this article, McMillen and Brown explained how the odd-colored card could be sighted while riffling for the division of the deck in preparation for an in-the-hands riffle shuffle. (The trick was curiously reprinted as “Tell Tale Color” in The Sphinx, Vol. 39 No. 10, Dec. 1940, p. 247.)
Milbourne Christopher published the idea of spotting a single selection resting in a different colored bank during the interlacing of the cards for a tabled riffle shuffle in Hugard's Magic Monthly, Vol. 18 No. 9, May 1961, p. 99, and quotes from private notes made by Jean Hugard on July 18, 1934. Those notes, though, are predated by four months by the above The Sphinx citation.
Gordon Bruce has built on all this, with an elegant strategy for sighting two selections, using a push-through shuffle. It was published in Roberto Giobbi's Secret Agenda, 2010, p. 210.