What Causes Purple Colored Discharge During The Period?

First time ever wife had bright purple discharge during her period. Tried to do some research and there isnt too much except posts from sadly uneducated girls on what sex is, and ignorant @55 holes who make fun of their situation. But in any case from what I gathered this is normal and is due to clotting. Shes just freaking out, and im trying to do the good husband thing. And figure it out for her... Any help is appreciated