COUNTRY-WESTERN star Crystal Gayle sang "Don't it make my brown eyes blue." Now Levi Strauss & Co. could make her blue jeans brown.This holiday season, the world's largest apparelmaker will test-market jeans made from a naturally brown cotton denim. Ever since Levi Strauss began retailing the rugged pants to forty-niners during the California gold rush, the fabric has been woven from white cotton fibers dyed indigo blue. "Not only is the colored cotton a botanical breakthrough," says Roy Schiefner, Levi's product development manager, "but when woven [it] creates cloth that is incredibly soft, beautifully colored, and comfortable to wear." In addition, the color intensifies rather than fades over time. The jeans will first be marketed in California, East Coast markets, and a Levi's Only store in Columbus, Ohio. A more widespread back-to-school promotion will take place next August. Mr. Schiefner says that because colored cotton is "rare," the new Levi's Naturals jeans ($27 wholesale) will appeal to "a person who appreciates the new, unique, and fashion-forward." Actually, Indians in Peru and Central America have been using colored cotton for thousands of years. But the fiber is too short to be spun into yarn by machine, says Sally Fox, owner of Natural Cotton Colours Inc. of Wasco, Calif. Her company supplies the "Coyote brown" denim to Levi's. Ms. Fox was an entomologist and cotton-spinning hobbyist in 1982, when she obtained seeds for colored cotton that the United States Department of Agriculture had collected in the 1930s and '40s. After seven years of plant selection and cross pollination, she was able to achieve the necessary fiber length for a coarse yarn like that in denim. Forty farmers in Texas are growing the cotton on contract for Fox on some 1,200 acres, while Arizona farmers are growing another 400 acres' worth. "On the farmer's end, it's just like growing your regular production," says Eugene Bednarz, one of Fox's growers. "Until the time that it opens, a neighbor driving by doesn't even realize that it's not your regular white cotton." So far colored cotton yields up to a third less per acre. "This is so new, we're still studying that end of it," Mr. Bednarz says. However, farmers say that Fox pays them a fixed price around 2.5 times what white cotton now fetches. Huge harvests in the US and abroad and aggressive Soviet discounting have lately forced cotton prices down. No one else grows machine-spinnable colored cotton at the moment. This year's crop of 1,300 or so bales of trademark "Fox Fibre" will be less than 0.01 percent of the total US cotton harvest. Fox also grows green cotton, and is experimenting on other colors: yellow, pink, greenish-blue, reddish-brown, and rust orange. San Francisco-based Levi Strauss was taken private in a leveraged buyout in 1985. Sales of shoes, socks, pants, belts, shirts, and jackets for adults and children reached $4.2 billion last year.