Special kinds of cotton that grow fibers of green or brown have been around since the 1930s but only recently became commercially feasible when a long-fibered variety that can be spun by machine was finally bred
Since the cotton need not be dyed, processing plants avoid the expense of dyeing and the ecological hazards of getting rid of leftover dye and by-products
Green and brown cottons that can be spun only by hand are not commercially viable.