They were almost exclusively men who served in the Swedish Royal Life Guards. Apart from acting as decorative and exotic staffage figures in the Guards, they played trumpets and drums and served as footmen. Usually, when these men appear in the archives, they are baptized under the Lutheran faith.
During the baptism, the men were given new names. Apollo, Pluto, and Zenoni got Christian names like Carl Gustav, Johannes, and Fredrick. Sometimes, they were named after their godparents. In the summer of 1777, a man called Vulcain was baptized in the Royal Chapel (Stockholm Palace) and promptly named Gustaf Ludwig Magdalena Carl Hedwig Fredrik Albrecht. It is doubtful that he would have chosen all those names himself.
A black trumpeter who came to Sweden in 1770, probably from Boston, was baptized Carl Gustav Abrahamsson. However, in private, he appears to have continued using his former name, Richard.
The legal status of the royal servants seems unclear. Slavery was not allowed under Swedish law, but it is not hard to imagine that these men had little or no control over their own lives. It is documented, among other things, that they sometimes needed royal permission to get married, which, of course, was not commonplace. One such example is Peter Watkins Montese, a black servant to Queen Dowager Lovisa Ulrika. In 1776 he wanted to marry the chimney sweep's daughter Lovisa Dorothea Sundberg. When the priests objected on a purely racist basis, the matter was sent all the way up to the King for a royal decision. King Gustav III decided that there was no impediment to the marriage. Hence, Peter and Lovisa were married on 28 March that same year.
Sources
Information about Vulcain can be found at https://tidningar.kb.se
Read more about Abrahamsson in Arvid Bergman's book 'Född slav - död Fri?' (2018) (Born a slave, dead free?)
Documents relating to Montese are available from Stockholmskällan