Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear sister, thank you for your question and for your interest in performing Prayers and fasting, two of the pillars of Islam.
As for your question, this blood is a part of your menstruation. So, you have to make up for this day and wait till the blood stops.
Responding to your question, Dr. Muhammad Salama, PhD in Islamic Studies in English and an Assistant Professor at the Faculty of Islamic Science, Al-Madinah International University, states,
Yes, sister, this blood is of your menstruation as sometimes the usual menstrual period changes. So, you need to wait until the blood stops and make sure that you are clear and then start praying and fasting.
Of course, your fasting today has become invalid.
Allah Almighty knows best.