I'm in my early 30's and can remember a time when my period was light and I had not pain ... but it changed sometime a few years back and became VERY painful for a day.
I'm not sure if your symptoms point toward a disorder, or not. But you might be wise to visit your OB GYN to seek advice about the changes (color of the blood and severe pain). Can you describe the pain a little better? (Location, possible source, duration, etc.)