White flag of the Merinid and Saadi dynasties
Own work based on:

Bennison, Amira K. (2014). "Drums, Banners and Baraka: Symbols of Authority during the First Century of Marīnid Rule, 1250–1350*". The Articulation of Power in Medieval Iberia and the Maghrib: 194–216.:"Although white is cited as the colour of the Umayyads, of the Almohad caliphal standard, and of the Marinid sultan's banner, it is not clearwhether such white banners included religious inscriptions and designs or not. The Marinid sources simply refer to white as the dynasty's colour."/"The naming of the Marinid palatine city, Madīnat al-Bayḍā', the White City, reflects their use of white as a dynastic colour which, of course, contrasted with the naming of the Nasrid capital, Madinat al-Ḥamra', the Red City, and their flag, described as vermilion with Arabic inscriptions in gold."
III, Comer Plummer (2015)    (in English)   Roads to Ruin: The War for Morocco in the Sixteenth Century, Lulu.com, pp. 26  ISBN:  978-1-4834-3105-5. : "It was unconventional to be sure, as was the Saadian standard, a dramatic statement in white, richly embroidered in golden Qur'anic verses. The white standard was an old Merinid tradition bestowed by the sultan upon faithful commanders. But, as a king in his own right, and in eschewing the familiar green of Islam, Mohammad ash-Shaykh made it look so very new."
Smith, Whitney; Internet Archive (1975)    (in English)   Flags through the ages and across the world, McGraw-Hill, pp. 254  ISBN:  978-0-07-059093-9. : "From the eleventh century until the beginning of the seventeenth, the principal color was white under the Almoravids, Marinids, and Saadians."
Boudouma, Jamal (2007). "Identité. L’hymne et la bannière". TelQuel (262).:"The Almohads, like the Saadis later, kept the same white standard, while the Marinids added a six-pointed star."
Abitbol, Michel (2014)    (in French)   Histoire du Maroc, Éditions Perrin  DOI:  10.3917/perri.abitb.2014.01. ISBN:  978-2-262-03816-8. :"al-Ifrani, who also notes the presence of many valuable horses in these parades, as well as standards of several colors including the white banner of the sultan [Ahmed al-Mansour]" Check: al-Ifrānī, Muḥammad as-Suġaiyir (1888)    (in Arabic)   Nuzhat al-ḥādī bi-aḫbār mulūk al-qarn al-ḥādī: Nozhet-elhâdi, histoire de la dynastie Saadienne au Maroc (1511 - 1670), Leroux, pp. 117  .
Palomares, Lucien (11 July 2012)    (in French)   Tarik es Salama, Lulu.com, pp. 266  ISBN:  978-1-4717-8163-6.  :"Les dynasties précédentes,  Mérinides et Saadiens, utilisaient le drapeau blanc."
العزيز, بنعبد الله، عبد (1957)    (in Arabic)   مظاهر الحضارة المغربية, دار السلمى،, pp. 43  : "As for the flag, it was white at the beginning of the Islamic era, by analogy with the flag of the Fatimids and Umayyads (unlike the Abbasid flag, which was black and then blue. The flag of the princes of Sanhaja was multi-colored, but it became white in the days of the Almohads, Marinids, and Saadians. Then the Alawites chose red."
رزق, عاصم محمد (2006)    (in Arabic)   رايات الإسلام, مكتبة مدبولى الصغير, pp. 151  ISBN:  978-977-208-544-6. : "1/10- White standards and flags: Ibn Khaldun, when talking about the flags he saw during the days of Sultan Abu al-Hasan al-Zanati, indicated that they used to give governors, workers, and commanders permission to take one small flag made of white linen (504). Al-Qalqashandi mentioned white flags in two places, the first of which was when he spoke about the Almohad flag in Tunisia, and he stated that: It was a white flag called the Victorious Flag, and it was raised in front of their sultan when riding it for the Eid prayers or for travel by the slaves of the Makhzen (who are the common people of the country and the people of the markets). The second of them is when he talked about the sultanate’s emblem among the kings of the Banu Abd al-Haqq of the Banu Marin in Morocco, or when their sultan went out to travel, and he mentioned it in it. It includes a white flag made of silk with verses from the Qur’an written in gold at the top of the circle. They call it the Victorious Flag (505), and Al-Hasan bin Omar indicated that the kings of Morocco had a white flag (506)."
Markham, Sir Clements (15 May 2017)    (in English)   Book of the Knowledge of All the Kingdoms, Lands, and Lordships that are in the World: And the Arms and Devices of each Land and Lordship, or of the Kings and Lords who possess them. Written by a Spanish Franciscan in the Middle of the XIV Century. Published for the First Time with Notes by Marcos Jiménez de la Espada, in 1877, Taylor &amp; Francis  ISBN:  978-1-317-17331-1. : "I departed from CEPTA and went to the noble city of FEZ where the Kings of the BENA MARIN always reside4. There runs past it a river called FEXE which rises in the clear mountains, and falls into the western sea near a city called CALES. At FEZ their Kings are crowned and reside, and they have a flag all white. (See Plate XIII, 57.)"
Nourerrahmane