Black hair that sprouts in a nega of the hair or beard protects against yellow hair and spreading, regardless of whether it was gathered together or scattered, surrounded by the nega or not. Black hair that remains from before the nega appeared protects against yellow hair and spreading, regardless of whether it was gathered together or scattered, or surrounded by the nega, but not when it’s off to the side unless it’s distant from the standing hair by the distance of two hairs. If one hair is yellow and the other is black, or if one is yellow and the other is white, they don’t protect against the nega.
Yellow hair that preceded a nega of the hair or beard is ritually clean. Rabbi Yehuda says that it’s unclean, while Rabbi Eliezer ben Yaakov says that it doesn’t transmit impurity nor does it provide protection against impurity. Rabbi Shimon says that anything in a nega of the hair or beard that isn’t a sign of impurity is a sign of ritual purity.