If you are a young Teen or Adult, from my past experience and what I told my daughters. (I have 3), after your menstrual cycle you will have some "residual" in your "system". The blood tends to turn brownish or a dark burgundy color. When you go to the restroom some of this will also be released. If you are having other issues going on, you may want to go to your doctor. You may also want to speak to your mom, auntie, school nurse, etc.
Best of luck.
Best of luck.