OPINIONS: The Mishnah discusses five colors of Dam Nidah. The Rishonim point out that all five types of blood are Tamei mid'Oraisa (see TUR YD 188:1). The Rishonim write, however, that since we lack the expertise of the earlier sages, any blood that has a tendency to a red or black color is also Tamei. The Poskim discuss some of the colors that are not mentioned in the Mishnah explicitly.
(a) YELLOW. When the Mishnah records an argument about blood that is "Yarok," it is not referring to the color green (as "Yarok" means in modern Hebrew). Blood that is green like a leek or grass certainly is Tahor, even if it has the consistency of blood, even according to Akavya (TOSFOS DH ha'Yarok, ROSH, RAN, RASHBA). The argument in the Mishnah is about whether blood the color of yellow or gold is Tamei. Tosfos compares the color Yarok to an Esrog or to wax, while the Rosh compares it to the yellow of an egg. Moreover, the Rishonim cite a number of verses in Tanach (see Tehilim 68:14) and Midrashim (see Midrash Rabah 43:2 on Bereishis 14:14, and Tosefta Nega'im 1:3 on Vayikra 13:49) to prove that Yarok is yellow and not green.
Since the Chachamim in the Mishnah rule that Yarok is Tahor, the Halachah should follow their opinion, and blood that is yellow should be Tahor.
It is interesting to note that TALMIDEI RABEINU YONAH in Berachos (22a of the pages of the Rif) quote a different opinion about whether yellow blood is Tamei or Tahor. Rebbi Zeira (Berachos 31a, Nidah 66a) says that women nowadays are stringent to observe seven days of Tum'ah after seeing "even a drop of blood like a mustard seed." While most understand that this refers to the amount of blood (i.e. the size of a mustard seed), the opinion quoted by Talmidei Rabeinu Yonah explains that this means that women consider even blood the color of mustard (yellow) to be Tamei. Talmidei Rabeinu Yonah agree with this explanation, and they even assert that the Mishnah says that blood the color of mustard is Tamei. (It is not clear to which Mishnah they are referring. Apparently, they understand the Mishnah on 40a, "Afilu k'Ein ha'Chardal" -- to be referring to the color of mustard, and not to the size of a mustard seed.)
(b) BROWN. The CHOCHMAS ADAM rules that blood the color of chestnuts or black coffee is Tahor. Other Poskim write that different shades of brown have different rulings, based on how close they are to red (MAR'EH KOHEN 2:1).
HALACHAH: With regard to yellow, the CHOCHMAS ADAM (117:9) writes that out of doubt, at least for a Hefsek Taharah, gold or wax-colored blood which has a tendency towards the color orange should be deemed Tamei. His opinion is based on earlier Acharonim who hesitated before being Metaher Bedikos of this color (since it is so close in color to orange). Contemporary Poskim are divided as to whether to accept the stringency of the Chochmas Adam (see MAR'EH KOHEN 2:2).
Of course, with regard to these and all other questions regarding a doubt in the laws of Nidah, a competent Halachic authority must be consulted. One should bring to the Posek all Mar'os and Bedikos that are even slightly questionable. In addition to ensuring that one is properly fulfilling the laws of Nidah, by bringing all questionable Mar'os to a Posek one will eventually become knowledgeable in determining which Mar'os need the ruling of a Posek and which do not.


QUESTION: In the Mishnah (19a), the Tana Kama appears to express the same opinion as Rebbi Yosi, who is quoted later in the Mishnah. The Gemara asks why the Mishnah quotes Rebbi Yosi at all, as his opinion seems repetitive, since the Tana Kama already expresses that view. The Gemara answers that the Mishnah's intent is to teach that the Tana Kama is Rebbi Yosi. Why, though, do we need to know that the Tana Kama is Rebbi Yosi? The Gemara answers that there is a principle that when one relates a teaching in the name of the one who originally said it, he brings redemption to the world.
The source for this principle is a verse in Megilas Esther. The Gemara in Megilah (15a) quotes Rebbi Elazar who derives this principle from the verse, "And Esther said this to the king in the name of Mordechai" (Esther 2:22). Because Esther humbled herself and mentioned the source of her information (that Bigsan and Teresh were conspiring to assassinate the king) to Mordechai, and she did not attribute the information to herself, the Jewish people were saved from Haman in her merit.
How, though, can we derive this principle from Esther? Perhaps the reason why redemption came about at that time was that the king recorded Mordechai's name in his ledgers in order to pay him back at a later time. Eventually, the fact that the king owed his life to Mordechai led to the salvation of the Jewish people. How does the Gemara learn from there that every time one relates a teaching in the name of someone else, he brings redemption to the world? (See RIF in EIN YAKOV, Megilah 15a, who leaves this question unanswered.)
(a) The IYUN YAKOV in Megilah understands the Gemara in Megilah as follows. Logically, Mordechai should have given his information personally to Achashverosh, so that the king would have more gratitude to him. Why did Mordechai tell Esther to give the information to Achashverosh? Rebbi Elazar understands that this must have been because Mordechai knew that whenever one says something over in the name of someone else, he brings redemption to the world. This is why Mordechai told Esther to relay the information in his name and did not tell Achashverosh himself. From here we learn that this is an established way to bring redemption.
(b) The ETZ YOSEF in the name of the MANOS HA'LEVI gives a different explanation for the Gemara in Megilah. He says that Mordechai actually wanted Esther to say the information in her own name in order to help boost her standing with the king. However, Esther was very humble and did not want to make use of this favor for her own prestige, and instead she attributed the information to Mordechai. This trait of humility and shunning honor is a trait of Mashi'ach, who is described as "a poor person riding on a donkey." A true redeemer knows that he is not the power behind redemption, but rather that he is merely a messenger of Hash-m.
According to the Etz Yosef, it seems that this principle applies only when a person is quoting someone else in order to give that person credit, but not when he is strengthening his own position by quoting the other person. It is possible that this explanation answers a question on the Gemara here in Nidah as well. Even according to the Gemara's answer -- that the Mishnah is teaching that the Tana Kama is Rebbi Yosi, why does the Mishnah not say simply, "Divrei Rebbi Yosi" -- "these are the words of Rebbi Yosi," after expressing his opinion? Why does the Mishnah need to quote his opinion a second time? Perhaps the answer to this question is that the Mishnah has already been established to be expressing an argument between the Tana Kama and Rebbi Meir, and one presumably would rule like the Tana Kama even without the need to mention Rebbi Yosi. The only reason why the Mishnah mentions Rebbi Yosi is to give him the credit for the authorship of this statement. Accordingly, this is an example of how to bring redemption to the world.
(c) The TORAH TEMIMAH (to Esther 2:22) writes that this principle teaches nothing out of the ordinary. It merely relates that when a person's name is given as the source of information, it is possible that positive things will occur due to the information being attributed to him. Rebbi Elazar in Megilah uses the word "redemption" because that is the positive event that happened at that time, in the case of Esther and Mordechai. However, he does not mean that "redemptions" will always occur when one says something in the name of someone else.
However, the Gemara here seems to conflict with the explanation of the Torah Temimah. The Gemara says that the only reason why the Mishnah quotes Rebbi Yosi is in order to bring redemption to the world. Had there been a Halachic reason to quote Rebbi Yosi, the Gemara would have mentioned that reason. If there is no special merit in listing Rebbi Yosi as the author of this opinion, then what type of positive event is supposed to occur due to the attribution of the statement to Rebbi Yosi in the Mishnah? Moreover, the Gemara in Pesachim (3b) says that a person should always teach his student in the shortest manner possible. This was especially applicable when the Mishnayos were being taught orally and not written down, in order to lessen the amount of words that the student needed to memorize. If there is no Halachic reason to add that the author of this opinion is Rebbi Yosi, and there is no obvious positive outcome of mentioning it, then why should the Tana of the Mishnah require students to memorize Rebbi Yosi's statement separately? According to the Torah Temimah's understanding of the principle of "Mevi Ge'ulah l'Olam," this principle should not override the necessity of brevity. The Torah Temimah's understanding, therefore, needs further clarification in light of the Gemara here. (See Insights to Nazir 56:2.) (Y. MONTROSE)