If you feel that your period is not your normal, it is recommended to see your doctor. You know your body best!
The colours you are most likely to see during your period are:
Bright red – this shows up for the longest amount of time during most people’s periods.
Dark red – this colour is associated with heavy days, first thing in the morning, and clots. This colour will only be seen at some points during the period, not the whole time. If this colour is the dominant one, get it checked out. Heavy periods might indicate anemia.
Brown or black – this colour is usually at the beginning or end of the period, and it’s just the old blood that has been oxidized the longest. If this colour is the dominant one, get it checked out.
Pink – this colour is mildly unusual. It might mean the flow is very light, that estrogen levels are low, an unbalanced diet, or that a high level of exercise is shortening the period. Not all of this is bad! However, if this colour is the dominant one, get it checked out.
Any other colour (in my research for this, blue, purple, orange, and grey have all been mentioned) should be seen by a doctor asap, as they indicate some health issues.
Any bleeding in between periods should be checked out asap as well, as that could indicate other health problems.
References
Trying to find good, sourced references on this topic was very difficult. I’d find an article that told me all about the colours of the blood, but then there’d be no references in the article, and I’d have to start all over again. Very frustrating!
http://www.webmd.boots.com/women/guide/menstrual-blood-problems-clots-colour-and-thickness
http://www.healthline.com/health/womens-health/why-is-my-period-brown#1
http://www.teenvogue.com/gallery/period-blood-colors-what-they-mean
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