Almoravid black flag
Own work based on:

Bel, Alfred (1903)    (in French)   Les Benou Ghânya: derniers représentants de l'empire Almoravide et leur lutte contre l'empire Almohade, E. Leroux, pp. 131  : "The Almoravids always had black standards and we know that black was also the color of the first Abbasids. We do not think that we can see in the adoption of this color by the Almoravids a means of marking their attachment to the Abbasid caliphate... We think that into the black color of the Almoravid standards, we must see a symbol, the interpretation of which Mr. Van Vioten very clearly explained: The black color of the standards marks the fight against impiety and error, he says, according to the poet El-Komaït; in addition, the black flags represent the flag of the Prophet, to which all our sources agree to attribute the color black. Cf. Research on Arab Domination, Chitism and Messianic Beliefs under the Umayyad Caliphate, Amsterdam, 1894, p. 64. This is enough to show us how, from the start, the Almoravids were able to adopt the black flag, to clearly mark the religious character of their invasion."
PAQUIS, M. (1836)    (in French)   Histoire d ́Espagne, depuis l ́an 1157 jusqu ́à la mort de Charles III...depuis l ́avénament de Charles IV jusqu ́à la mort de Ferdinand VII par M. Dochez, Parent-Desbanes, pp. 672  : "provided with white flags (those of the Almoravids were black) and placed them under the orders of Abu Muhammed Albaschir, one of the decemvirs."
(in French) (1843)  Mémoires de l'Académie royale de Metz, Lamort, pp. 127   :"their standard is a white flag in hatred of that of the Almoravids, which is black."
Dollfus, Lucien (1894)    (in French)   Études sur le moyen âge espagnol, E. Leroux, pp. 168  : "Definitely crushed, after a furious melee, he disappeared at a gallop from his horse (1208). The white flag overthrew the black flag. Winners in Africa, the Almohads attacked the Balearic Islands where the last Almoravid reigned, Abdallah, brother of el Mayorki."
El-Hibri, Tayeb (22 April 2021)    (in English)   The Abbasid Caliphate: A History, Cambridge University Press, pp. 218  ISBN:  978-1-107-18324-7. : "From far-off Maghreb, an emissary of the Almoravid Ali b. Yusuf b. Tashfin came to Baghdad in 498/1104 declaring allegiance to the Abbasids, announcing the adoption of the official Abbasid black for banners, and received the title Amir al-Muslimin wa Nasir Amir al-Mu'minin ("prince of the Muslims and helper of the Commander of the Faithful")."
(in English) (2010)  The Chronicle of Ibn Al-Athir for the Crusading Period from Al-Kamil Fi'l-Ta'rikh, Ashgate Publishing, Ltd., pp. 311  ISBN:  978-0-7546-6951-7. : "The Almoravids took camels and made them like fortresses, fighting alongside them, and they made the black Abbasid flag their emblem"
Būtshīsh, Ibrāhīm al-Qādirī (1993)    (in Arabic)   المغرب والأندلس في عصر المرابطين: المجتمع، الذهنيات، الأولياء (Morocco and Andalusia in the Almoravids era: society, mentalities, saints), دار الطليعة،, pp. 80  : "The color of the veil also changed from the blue color that prevailed before the beginning of the Almoravid call (2) to the color black. This is an obvious thing if we know that the Almoravids adopted all the symbols of the Abbasids, including the color. Al-Aswad, on the other hand, confirms that the Almoravids’ connection with the Abbasids began from the very beginning of their movement, which reinforces the idea of the fluidity of the Sunni tide in the Islamic world, east and west."
محمد, حسن، (1999)    (in Arabic)   المدينة و البادية بإفريقية في العهد الحفصي, جامعة تونس الأولى، كلية العلوم الانسانية و الاجتماعية،, pp. 49  ISBN:  978-9973-922-48-9. : "When the Almoravid took control of Ifriqiya, he suppressed the khutbah in the name of 'Abd al-Mu'min's descendants and proclaimed the name of the Imam al-Naşir li-Din Allah, the Abbasid caliph, to whom he sent requesting robes of investiture and black banners."
Nourerrahmane