Do slaves wear just brown clothes, or do they were what they can find? How does a person get put in the save trade? Like, do they go to some place where they buy slaves?
You might want to read these: https://arheo.ffzg.unizg.hr/ska/tekstovi/slavery_freedom.pdf https://www.medievalists.net/tag/slavery/
they'd wear whatever they were given by their masters or what they were wearing when enslaved, and they'd generally either be enslaved by force, or in some cases by being sold by families ,or by debt. With my mod hat on, for everyone reading, this is a very flammable subject at the moment - there is no problem with discussing it as pertains to writing, but we are not having a general debate about the ills of slavery... just be mindful that this is a writing thread and the staff are watching
It also depends somewhat on the time, place and conditions of slavery. For example, a palace slave might be well clothed, whereas a slave who worked in the fields might rely on a cottage industry within the slaves' own community who provided clothes.
The film Amistad has an excellent (albeit very disturbing) segment showing how an African man was kidnapped from just outside of his home, sold to slavers, endured the Middle Passage, and was eventually put up at auction in what is now Cuba. I used to use it in one of my History classes. I'm not posting the link here because it will move you to tears, but if you search youtube for things like Amistad Middle Passage you'll find it. It's disturbing as hell. And as for clothes, yeah, the enslaved people would almost certainly be given something inexpensive and durable, but I doubt the clothes were replaced very often. Enslaved people in the United States were allowed to go about their own daily activities after dark, on Sundays, and on Christmas, so the making and mending of clothing would have been an important activity.