Halakhah zu Negaim 3:7

From the laws of the commandment is that which they, may their memory be blessed, said (Sifra, Tazria, Parashat Nega'im, Chapter 13:1) that only clothes of wool and flax alone become impure with aliments; and the measure of their impurity is a split bean, like the measure in a person. And there are three signs of impurity with them (Mishnah Negaim 3:7): deep green; deep red; and spreading - the understanding of deep green is green among the greens, like the wing of a peacock; and of deep red is red among the reds, like crimson fabric. And the laws of spreading (Mishnah Negaim 11:7); the law of green that spread red or red that spread green; the law that all [cloths] are fitting to become impure - as they, may their memory be blessed, said (Mishnah Negaim 11:11) that it becomes impure with ailments, even though it does not become impure as the base (midras) of a zav - like sails of a ship, a partition, the decorative piece of a hairnet, scribes' hankerchiefs, a belt, the laces of a shoe or of a sandal that has the width of a split bean, and similar to them, and there is no need to say other [cloths] like bedspreads and pillows; and the rest of its details are elucidated in [the Order] of Tahorot, and most of them are in Tracate Negaim (see Mishneh Torah, Laws of Defilement by Leprosy 12).