So this is not an accurate translation. In this Hadith, the exception the Prophet (s) makes is three:
1- Amama which is the turban
2- Kesaa’ which is basically the cloak
3- Khoff which is not socks, but it’s a type of shoes made from leather. Some scholars have said it can include the socks as well. So that would mean it’s ok for the shoes/socks to be black (it wouldn’t be Makrouh). But it doesn’t mean that it’s Mustahab to wear black socks. It’s just not Makrouh.
And it is Mustahab for the arms to be covered.