For anybody interested:

"Duine gorm" was the Classical Irish term, seen in some 16th century MSS, although usually in a case form of "fear gorm".

This follows on from a Middle Irish usage of "gorm" to mean tanned. Old Norse similarly used its word for "blue" to mean tanned.

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The dialect I use is Munster Irish, particularly Cork Irish, so words or phrases I use might not be correct for other areas.

Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal

Thank you. I didn't know the origin. I suspect it was used all over Ireland. Dónall Bán Ó Céileachair has "fear dubh" in Aodh de Róíste, and I've been told "na daoine dúbha" is what they say in Corca Dhuíbhne. Cnósach Focal ó Bhaile Bhúirne has "ráigiúnach", but doesn't say whether it was pejorative or not. I suspect, there being few black people in Ireland before a certain date, that it was not pejorative.

Almost certainly not pejorative I'd say since it basically translates to "Region-er" or something similar, i.e. one from the far regions. It'd be used for anybody not Western European I think, though not a common word now.
Some people in Kerry today say "Duine Gorm" but it's hard to know if that's under influence from elsewhere. I'd say it went from "Gorm" to "Dubh" in Munster and is now going back.

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The dialect I use is Munster Irish, particularly Cork Irish, so words or phrases I use might not be correct for other areas.

Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal