All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If the azan for the Maghrib prayer is called in your area after sunset, then you must break your fast as soon as you hear the azan. The red light that remains on the horizon does not affect the time of breaking the fast because such a red light stays for a while after the sun sets.
Allaah Knows best.