There is a difference of opinion in regards to the complexion of Muslim Ibn Khalid Al Zanjy but for now we will try to understand the language given in his descriptions and deal with the most authentic description later in shaa Allah
….. Abu Abdul Rahman said to Suwayd why was he named Al Zanjy , he said because he was intensely black
حدثنا عبد الله ثنا سويد بن سعيد في سنة ست وعشرين ومائتين ثنا مسلم بن خالد الزنجي قال أبو عبد الرحمن قلت لسويد ولم سمى الزنجي قال كان شديد السواد
Abu Al Fadl Al Muhammed Ibn Taaher Ibn Ali Ibn Ahmed Al Muqaddasi As Shaybaany said in his book al Insaab Al Muttafigah Fee Al Khat Al Mutamaathilah Fee Al Nafd Wa Al Dhabt
Muslim Ibn Khaalid Al Makhzoomy their mawla, Abu Khaalid Tayaa Al Makky the jurist know as Al Zanjy. Ishaq AlHarby said it is because he was very white skinned so the opposite was used ( meaning he was so white that they called him the opposite which is jet black ) and Sawayd Ibn Saeed said he was Adam Shadeed Al Udmah ( jet black )
مسلم ابن خالد المخزومي مولاهم أبو خالد طيا لمكي الفقيه الامام المعروف بالزنجى قال اسحق الحربى لانه أشقر بالضد وقال سويد ابن سعيد كان شديد الادمة
Imam Al Dhababi confirms his understanding of the term Adam Shadeed Al Udmah here:
Imam Al Dhahabi said in his book Seera A’laam Al Nubalaa Chapter 11
Sawayd said he was named Al Zanjy because of his blackness. And others were in opposition to Ibn Saeed and other than him and they said he was Ashqar ( very white) and he was only given the nickname Al Zanjy to be opposite .
Ibraheem Al Harbi said he was a Makkan jurist and he was Ashqar (very white ) like an onion
Ibn Abi Hatim said he was an a leader in knowledge and Islamic Jurisprudence , he was white with some redness and was nicknamed Al Zanjy because of his love for dates , his female slave said to him : You are nothing but a Zanjy.
قال سويد بن سعيد : سمي الزنجي لسواده . كذا قال : وخالفه ابن سعد وغيره ، فقالوا : كان أشقر ، وإنما لقب بالزنجي بالضد . قال أحمد الأزرقي : كان فقيها عابدا يصوم الدهر . قلت : تفقه بابن جريج
قال إبراهيم الحربي : كان فقيه مكة ، وكان أشقر مثل البصلة .
وقال ابن أبي حاتم : إمام في العلم والفقه ، كان أبيض بحمرة ، ولقب بالزنجي لحبه للتمر . قالت له جاريته : ما أنت إلا زنجي
Ibn Al Jawzy gives the same three reasons and opinions too but uses the term Aswad which means jet black
With Al Zanjy there are three sayings…..The third ( saying) verily he was Aswad ( jet black )….I said to Suwaid , why was he named Al Zanjy and he said because he was intensely black.
بالزنجي ثلالة اقوال ….الثالث: أنه كان أسود…….. قلت لسويد لم سمي الزنجي قال كان شديد السواد
The Zanj were a race of people known to be jet black in colour hence why the term Al Zanjy was used. One of the descriptions given for him was Adam Shadeed Al Udmah which is another proof to show that it meant jet black.
Zanj does NOT translate to mean Negro!
Remember Imam Al Dhahabi mentioned this before that Adam Shadeed Al Udmah means jet black.
Imaam Al Alaamah Al Dhahabi says in his book Seera A’laam Al Nubalaa Chapter 2 page 168
‘They say Aswad (jet black) and this means whoever is covered in blackness. They say jet black or Shadeed Al Udmah.”
سير أعلام النبلاء ج٢ ص ١٦٨
قالوا اسود و كذا كل من غلب عليه السواد قالوا اسود او شديد الادمة
Read more about the meaning of Adam Shadeed Al Udmah here
More on the relationship between the blackness the people of al Al Zanj and the people of the Hijaaz (Arabs in Mecca, Medinah, Taif, etc)
And it is said that Muslim Ibn Saeed Ibn Jarjah and he was ethnically from As Shaam in origin and he was a beautiful white complexion
….And he was only called Al Zanjy because he was white with some redness (very white skinned) for this reason they called him Al Zanjy to mean the opposite because the people of Al Hijaaz had As Sumarah in them
ويقال مسلم بن سعيد بن جرجة، وأصله من الشام، وكان أبيض مليحا
روى عنه ابن المبارك والشافعي والحميدي وأحمد بن عبد الله بن يونس، وإنما قيل له: الزنجي لانه كان أبيض مشربا بحمرة فلذلك قيل له: الزنجي – على الضد لان أهل الحجاز فيهم سمرة
Again we see here Asamaani may Allah have mercy upon him makes record of the understanding of As Sumurah and how it was used to mean blackness and that it is a complexion opposite to the whiteness of the Persians and Romans and that the people of Al Zanj fit into the category of As Sumurah similar to the Arabs!