Original post by I7V1. His Musnad was an early collection of hadeeth, not many have survived which were before it. I haven't found a wording of this hadeeth which has no mention of black and white which precedes the Musnad. Even if there is one, it is not an evidence that it is a later addition - it may be that the later Hadith had more reliable narrators. The quality of the hadeeth doesn't lie in the conciseness of the chain, rather it is in the reliability of the narrators.
2. The word 'ahmar' is used, which literally means red. In Siyar A’laam Al Nubalaa, Chapter 2, page 168, Imaam adh-Dhahabi (died 1348CE) said:
“Red, in the dialect of the Arabs means a pale white complexion and it was a colour that was rare amongst them.”
الحمراء ، في خطاب أهل الحجاز : هي البيضاء بشقرة ، وهذا نادر فيهم
He then went on to explaining why and gave an example quoting the part of a long hadith which can be found in Bukhari Book of Oaths –
حَدَّثَنِي أَبُو الرَّبِيعِ الْعَتَكِيُّ، حَدَّثَنَا حَمَّادٌ، – يَعْنِي ابْنَ زَيْدٍ – عَنْ أَيُّوبَ، عَنْ أَبِي، قِلاَبَةَ وَعَنِ الْقَاسِمِ بْنِ عَاصِمٍ، عَنْ زَهْدَمٍ الْجَرْمِيِّ، – قَالَ أَيُّوبُ وَأَنَا لِحَدِيثِ الْقَاسِمِ، أَحْفَظُ مِنِّي لِحَدِيثِ أَبِي قِلاَبَةَ – قَالَ كُنَّا عِنْدَ أَبِي مُوسَى فَدَعَا بِمَائِدَتِهِ وَعَلَيْهَا لَحْمُ دَجَاجٍ فَدَخَلَ رَجُلٌ مِنْ بَنِي تَيْمِ اللَّهِ أَحْمَرُ شَبِيهٌ بِالْمَوَالِي فَقَالَ لَهُ هَلُمَّ . فَتَلَكَّأَ فَقَالَ هَلُمَّ فَإِنِّي قَدْ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَأْكُلُ مِنْهُ . فَقَالَ الرَّجُلُ إِنِّي رَأَيْتُهُ يَأْكُلُ شَيْئًا فَقَذِرْتُهُ فَحَلَفْتُ أَنْ لاَ أَطْعَمَهُ فَقَالَ هَلُمَّ أُحَدِّثْكَ عَنْ ذَلِكَ إِنِّي أَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فِي رَهْطٍ مِنَ الأَشْعَرِيِّينَ نَسْتَحْمِلُهُ فَقَالَ ” وَاللَّهِ لاَ أَحْمِلُكُمْ وَمَا عِنْدِي مَا أَحْمِلُكُمْ عَلَيْهِ ” . فَلَبِثْنَا مَا شَاءَ اللَّهُ فَأُتِيَ رَسُولُ اللَّهِ صلى الله عليه وسلم بِنَهْبِ إِبِلٍ فَدَعَا بِنَا فَأَمَرَ لَنَا بِخَمْسِ ذَوْدٍ غُرِّ الذُّرَى قَالَ فَلَمَّا انْطَلَقْنَا قَالَ بَعْضُنَا لِبَعْضٍ أَغْفَلْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم يَمِينَهُ لاَ يُبَارَكُ لَنَا . فَرَجَعْنَا إِلَيْهِ فَقُلْنَا يَا رَسُولَ اللَّهِ إِنَّا أَتَيْنَاكَ نَسْتَحْمِلُكَ وَإِنَّكَ حَلَفْتَ أَنْ لاَ تَحْمِلَنَا ثُمَّ حَمَلْتَنَا أَفَنَسِيتَ يَا رَسُولَ اللَّهِ قَالَ ” إِنِّي وَاللَّهِ إِنْ شَاءَ اللَّهُ لاَ أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَتَحَلَّلْتُهَا فَانْطَلِقُوا فَإِنَّمَا حَمَلَكُمُ اللَّهُ عَزَّ وَجَلَّ ” .
” ...A red man as if he is one of the slaves...’’
adh-Dhahabi said the explanation for this is:
”..and from it is the hadeeth that his color is like that of the slaves (mawaali) who were captured from the Christians of Syria and Rome”.
، ومنه في الحديث : رجل أحمر كأنه من الموالي يريد القائل أنه في لون الموالي الذين سبوا من نصارى الشام والروم
3. Narrated Anas bin Malik: Allah's Messenger (ﷺ) said, "You should listen to and obey, your ruler even if he was an Abyssinian slave whose head looks like a raisin."
I am not strong in the Arabic language so I do not know whether 'ka anna' here indicates that:
a) The Abyssinians themselves are described as having raisin-like heads.
b) This is an extra description, meaning: obey the ruler even if he was an Abyssinian slave and also his head looks like a raisin.
I don't know for sure which of the two is intended so I won't speak of what I have no knowledge about. Even if it was describing them having raisin-like heads, the hadeeth is a command to still listen and obey them like you would any other leader, not to belittle them. It is evident that the Prophet ﷺ and his companions did not have hatred towards black people merely for their colour as you can see with their relationship with Bilāl ibn Rabāh and other believers who were black (meanings of the ahaadeeth):
Abdullah ibn Muhammad reported: My father and I departed to see our father-in-law from the Ansar, visiting him as he was ill. The time for prayer arrived and he said to some of his relatives, “Young lady, bring me water for ablution that I might prayer and be comforted.” We objected to that from him, but he said, “I heard the Messenger of Allah, peace and blessings be upon him, say: Stand, O Bilal, and comfort us with the prayer.” [Sunan Abī Dāwūd 4986]
Abu Huraira reported: The Prophet, peace and blessings be upon him, said to Bilal at the time of dawn prayer, “O Bilal, tell me of the most hopeful deed you practiced in Islam. I heard the scuffle of your sandals before me in Paradise.” Bilal said, “The most hopeful deed to me is that I do not perform ablution by day or night but that I pray along with it as much as Allah has decreed me to pray.” [Ṣaḥīḥ al-Bukhārī 1149, Ṣaḥīḥ Muslim 2458]
Jabir ibn Abdullah reported: Umar, may Allah be pleased with him, used to say, “Abu Bakr is our master and he emancipated our master,” meaning Bilal. [Ṣaḥīḥ al-Bukhārī 3754]
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, told us about the Negus, the ruler of Abyssinia, on the day he died. The Prophet said to us, “Seek forgiveness for your brother.” [Ṣaḥīḥ al-Bukhārī 1263, Ṣaḥīḥ Muslim 951]
These are not statements and actions of people who hate people with black skin or Abyssinians. Your argument 'would be frowned upon today' is not a valid argument as many things are frowned upon today that were not back then. Does it make it objectively wrong? Maybe in that context it was a genuine description with no malicious intent and that is what is likely based on their treatment of the Abyssinians. Regardless of all of this, I don't see why you brought it up as the topic at hand was did the concept of black and white exist back then. There is no need to change to topic just to display your opposition to Islaam.