If you’ve had your period for a while, you know that it’s an ever-shifting adventure. When will it come? How heavy will it be this month? What colour will it be today? Isn’t it fun to be a woman?

The answer, usually, is that if you’re wearing white and/or have forgotten to replenish your supply of tampons, that’s when your period is most likely to start – and it will be heavy and bright red.

But did you ever wonder why your period is sometimes pink-tinged, and other times resembles road tar? It’s a veritable rainbow in your underwear one week of the month, and it turns out there’s a reason why. Dr Lisa Masterson, the obstetrician and gynaecologist who appears on the syndicated television showThe Doctors, calls periods “vital signs” that can tell us a lot about our health. So here’s a handy-dandy guide to the many colours of your period and what they mean…

Pinkish

If you’re lucky, the first sign of your period is pink on the toilet paper when you wipe, rather than a sudden wave of the Red Sea when you least expect it. That’s because at the very beginning of your period, when your body is just warming up for the main event, it’s common for your normal vaginal discharge to be a little pink-tinged.

Bright red

The first few days of your period, when the flow is fast and furious, it’s likely to be bright red. This simply means you’re seeing new blood that hasn’t had a chance to hang around getting old in your uterus. “Pink and red are normal,” says Dr Masterson. “That’s normal menstrual blood flow.” So whip yourself up an amazing snack and hunker down with your favorite terrible romantic movie.

Dark red