* WEDNESDAY Diamond Rio Celebrates Red Wing (TNN, 8-9 p.m.): The small Mississippi River town of Red Wing, Minn., had a big celebration this summer: the 90th anniversary of their Red Wing Shoes factory. The highlight of this ''Shoe-Bilee'' was a private outdoor concert by country powerhouse Diamond Rio, whose hit singles like ''Norma Jean Riley'' and ''In a Week or Two'' have earned it the Vocal Group of the Year award for three consecutive years by the Country Music Association. The Cronkite Report (Discovery, 10-11 p.m.): Walter Cronkite takes a hard look at the state of environmentalism in this program, entitled ''Environment Beware: Here Comes the Counterrevolution.'' Talking with key political figures such as Secretary of the Interior Bruce Babbitt and House majority whip Tom DeLay, Cronkite explores Congress's recent resistance to environmental regulation. He also approaches the issue from the standpoint of environmentalists, business leaders, and the American public, taking special note that the public's interest in the environment seems to be waning. * THURSDAY World of Audubon (TBS, 8:05-9:05 p.m.): Take a trip down the Grand Canyon with singer James Taylor, his son Ben, and environmentalist Martin Litton in ''Colorado River Adventure.'' Slow-motion white-water-rafting scenes punctuate more tranquil, beautiful shots of the canyon, during which the Taylors croon melodies nearly at one with nature. Litton, who has crusaded for the canyon's protection for decades, explains some of the environmental issues surrounding the area. * FRIDAY 20/20 (ABC, 10-11 p.m.): Barbara Walters interviews Gen. Colin Powell in his first formal interview since retiring as chairman of the Joint Chiefs of Staff. Among the topics to be discussed: the '96 presidential election and his new autobiography, ''My American Journey.'' Please check local listings for these programs. Stay tuned for Thursday's Monitor, which will synopsize new series on the networks this fall.