When CO Congressman Taylor listed his reasons for the change: "But Taylor may have found his most persuasive argument in the record of the U.S. Senate’s proceedings from 1861 when the Senate named the Colorado Territory. As introduced and passed by the House, the name in the bill for the proposed new territory was the “Territory of Idaho”, other names reportedly considered were Jefferson and Arcadia. In the Senate, however, the name “Idaho” was stricken and “Colorado” inserted “for the reason that the Colorado River arose in its mountains, hence there was a peculiar fitness in the name.” https://legisource.net/2021/05/06/the-mighty-colorado-river-once-known-as-merely-grand/