Sources: Non-Muslims and Clothing
Several Abbasid caliphs enforced draconian laws enforcing clothing restrictions on non-Muslims. Muslim society was class and difference-conscious, meaning everyone wore clothing that signalled their social class, their profession, or even their religious community. But the clothing requirements for non-Muslims was not a matter of style. Rather they were legally prescribed, and, as some primary sources demonstrate, specifically geared to subordinate and humiliate them.
Jewish scribes at Ezekiel's Tomb, in Al Kifl, Iraq, early 1900’s. Obviously not the same time period, but you can see the similarity in clothing. Robes, turbans, slipper shoes. Image source.
The rules could change according to the whim of the caliph or go entirely unenforced. Christians, Jews, Zoroastrians, and others likely wore distinctive outer clothing, but had a great deal of leeway. But it may also be the case that some wore no distinctive clothing at all at this time.
It’s still not clear to me what non-Muslims were supposed to wear during the period of the novels are set. Just because a legal scholar of the time argued it should be a certain way does not mean that others agreed with that jurist, or that his ruling was taken up by any enforcing body.
It might have been “honey-coloured” outerwear for all, or, as other sources argue, Jews should wear blue or yellow, Christians red, and Magians black. Dhimmi men seem to have worn a rope-like belt for a sash around their outer robe. Slaves of non-Muslims are supposed to have to worn coloured patches to mark the religion of their owners. In the books, I am assuming most wore distinctive clothing and am erring on the side of honey-coloured and sometimes blue.
With some exceptions, even in the most restrictive periods, non-Muslims worked alongside Muslims in every social class and were well-represented in caliphal administration, all types of business, scholarship, the sciences, and medicine. Rich non-Muslims flourished among the wealthy classes and the poor struggled alongside their peers. There was social mixing and inter-marriage, although Muslim women could not marry men of other faiths. Non-Muslims had their own neighbourhoods and justice systems although could make use of the Muslim justice system if they liked. While Muslims paid a yearly charity tax based on their income—the poor receiving the tax rather than giving it—non-Muslims paid a standardized poll tax not geared toward income. See Goitein’s A Mediterranean Society: The Jewish Communities of the Arab World, based on first-hand accounts of Jewish traders. And this account of two converts to Judaism in medieval Egypt by Moshe Yagur.
The books take place during the last days of the caliphate of al-Muktafi (r. 902-908). The Peace will be set during the reign of the next caliph, al-Muqtadir, who revived the earlier draconian laws and added some of his own. These restrictions and their effects on people’s everyday lives may be part of the story. But the novel will be set at the very beginning of the caliphate, when he was just a boy, so they may not have been enforced at that time. In the Derya Mack mysteries, socially distinct clothing will play a strong role.
See Anver Emon’ s unflinching account of the most restrictive rulings in “Dhimmis in Public: On Attire and Transport, in Religious Pluralism and Islamic Law: Dhimmis and Others in the Empire of Law, Stillman, Arab Dress: A Short History, Ahsan, Social Life Under the Abbasids
When googling dhimmi, take care. As you can imagine in the present climate, in which Muslims are portrayed as ready to storm the “Gates of Vienna,” popular and even some scholarly accounts of dhimmi laws can be politically charged and downright Islamophobic.
Anver Emon’s book, Religious Pluralism and Islamic Law: Dhimmis and Others in the Empire of Law, is the one you want to read.