1. The Mishnah discusses various colors of blood that are deemed Tamei.
2. The Gemara explains that when the verse states, "between Nega and Nega," it refers to arguments among the Chachamim with regard to Tzara'as.
3. The two verses of "her blood" teach that there are four colors of blood that are considered Tamei.
4. This explanation (see #3) is given by many of the Tana'im in the Mishnah.
5. There is a dispute about the meaning of the statement that red blood that is Tamei is like a wound.
A BIT MORE
1. The Mishnah demonstrates what shade of each color it is discussing by comparing it to something of that color.
2. For example, there is a dispute about whether an entire article of clothing that change a shade of color is ruled to be Tzara'as or is pure like a person who is completely covered with Tzara'as (who is deemed Tahor).
3. Even though the Mishnah says that there are five colors of blood that are Tamei, one of the colors listed in the Mishnah is black, which is red that turned to black. This is why there are only four natural colors of blood.
4. The Gemara uses it to explain the views of all the Tana'im who add other Tamei colors, such as Akavya ben Mehalalel and Beis Shamai.
5. Shmuel: It is like the blood of a slaughtered ox. Ula: It is like the blood that comes from the wound of a live bird. Zeiri: It is like blood from lice found on one's head.