Niddah, Chapter 10, Mishnah 1. This mishnah teaches through a mashal, and it is, in a sense, the working out of the pasuk "ishtecha kigefen poriyah", that a wife is compared to a fruitful vine. Here the comparison is put to practical use in describing what a woman's flow of blood can look like.
With that image in hand the mishnah begins: "Nashim bivsulaseihen kigefanim". In the years when a girl has not yet experienced any bleeding at all, the mishnah sets her alongside the vine. What the mashal comes to teach is diversity. Vines do not all bear alike, and neither does the bleeding of women follow one fixed pattern.
The mishnah then lists the possibilities: "Yesh gefen sheyeinah adom, veyesh gefen sheyeinah shachor, veyesh gefen sheyeinah merubah, veyesh gefen sheyeinah muat." Some vines yield a wine of a reddish hue, others a wine so dark that it is called black; some vines are generous in what they produce, and others give barely anything. The same holds for these early years of a woman's life: nothing here is predictable. The shade may vary and the amount may vary, and the way it appears in one woman is no guide whatsoever to another.
Rabbi Yehudah continues within the same mashal and adds an observation: "Kol gefen yesh bah yayin" - no vine is entirely without its wine. And should a vine turn out to produce none at all, "harei zeh dorketi", it is a shriveled, withered stock.
The nimshal is straightforward and sobering. Every woman is meant to menstruate; the flow is the sign of a healthy, living vine. If in the end no period comes at all, that itself is the indication that, Rachmana litzlan, this vine is dried up, that she is unable to bear children. Rabbi Yehudah is telling us that the wide variety the mishnah described, red or dark, plentiful or sparse, is all within the range of the normal. What lies outside that range is not a different color or a smaller measure, but the absence of any wine at all.