Does Shafaq denote the red or the white twilight?

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.

Shafaq is the red illumination or twilight that appears on the horizon slightly before sunset and lasts until the time of the ‘Ishaa' prayer. As the Shafaq disappears, the ‘Ishaa' prayer becomes due. The time for the Maghrib prayer lasts (from sunset) until the red twilight has faded. ‘Abdullaah ibn ‘Umar was reported to have said, "Shafaq is the red twilight; when it disappears, (the ‘Ishaa') prayer is due." [Al-Bayhaqi as   Marfoo‘ Hadeeth and ‘Abdur-Razzaaq as Mawqoof]

‘Abdullaah ibn ‘Amr also narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: "The time of the Maghrib Prayer is as long as the red twilight (Shafaq) has not disappeared."

Al-Mubaarakfoori said in his book, Tuhfat Al-Ahwathi, "There is no doubt that the preponderant opinion in this regard is that the Shafaq is the red twilight. This is supported by the Hadeeth of ‘Abdullaah ibn ‘Umar, may Allaah be pleased with them, as he narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said:  "Shafaq is the reddish twilight." [Ad-Daaraqutni] [Ibn Khuzaymah and others: Saheeh] [Ibn Khuzaymah in Buloogh Al-Maraam as Mawqoof]

Muhammad ibn Ismaa‘eel Al-Ameer As-San‘aani said that this is a linguistic matter and should be left for Arabic linguists to decide. Ibn ‘Umar was a high caliber linguist and one of the greatest Arabic linguists. His words constitute a strong proof even if the narration was Mawqoof (i.e. his own words and not a reported Prophetic tradition). End quote.

Imaam An-Nawawi said in Al-Majmoo‘, "According to our chosen opinion, Shafaq is  the red twilight as was narrated by Ibn Al-Munthir on the authority of Ibn Abu Layla, Maalik, Ath-Thawri, Ahmad, Ishaaq, Abu Yusuf and Muhammad ibn Al-Hasan . This is also the opinion of Abu Thawr and Daawood . On the other hand, Imaam Abu Haneefah, Zufar, and Al-Muzani believed that Shafaq is the white twilight."

Allaah Knows best.