Colored with large clots
If there are large clots present in your menstrual blood then this may mean that you have a low level of progesterone and high of estrogen.
The hormone levels are actually regulating our period so if there is something wrong with them that will affect the period as well. If the clots size is like a small coin then that is normal, but if they are bigger than that may be an indication to a condition called PCOS.
Usually, this coloration of the menstrual blood means anemia.
Our blood is getting the color from the red blood cells so if the color of the menstrual blood is pink then that indicates that your organism does not have the right density of red blood cells, so that may mean that you are having the condition called anemia.
Brown or rust colored
When our period is almost down, the blood flow is slow so the blood oxidizes and it gets this kind of color.
This is totally normal, as the blood at the beginning is red and at the end is brown/rust.
Dark brown or almost black
This kind of color appears usually if you are taking pills. This means that the blood is flowing down really slow and it does not get out of the body quickly. This is usually a situation when one woman is taking contraceptive pills because they have an effect on the hormonal levels.
The color of your period blood is a very important indicator if something is wrong with your body. Just do a regular check when you are at your period and follow the signs.