2,060. The Five Colors of Blood

Hilchos Issurei Biah 5:7

Five colors of blood render a woman ritually unclean: red, black, yellow, like muddy water and like diluted wine. All other colors are ritually clean.

Hilchos Issurei Biah 5:8

Red is the color of blood that flows first when people let blood. Such blood is placed in a cup and a stain is compared to it. Black is like dried ink. For yellow, fresh saffron is brought along with the soil in which it’s growing. One takes the middle stalk that is completely a stem from among quality stalks, each of which has three stalks with three leaves each. The stain is compared to the middle leaf on the middle stalk. “Like muddy water” refers to soil from the Sichni valley or similar places where the soil is red. Water is poured on it until the water is as thick as a garlic peel over the soil; there’s no specific volume of water or soil prescribed. These are stirred together in a vessel and compared to the stain while cloudy. If the water clears, it is stirred again to make it cloudy.