A question that I find it difficult to answer, as it will be based on anecdotal evidence and the at times selective (and manipulative) nature of news reporting.
So I offer these thoughts up, but take them with a large grain of salt:
Generalities
- Cities tend to be more cosmopolitan, and thus often have a wider, well-established racial mix. Whether this means a better reception, or merely less surprise at different skin colour / accent, I can't answer. Single females used to suffer unwarranted attention, but I sense that's eased off in recent years.
- Touristy locations are used to a wide variety of people visiting, and perhaps are less likely to even notice skin colour / accent (at times it feels they only care about the colour of money). Not places I particularly enjoy, but if safety is a concern on landing, then starting in a touristy location might not be a bad idea at all.
- Coastal tend to have a degree of tourism, but often more relaxed, though maybe the place most likely to experience unwanted attention for a single female?
- Countryside. Most relaxed IME, and certainly in Italy it seems to show the very best side of people, with genuine hospitality. Might attitudes be insular / suspicious? FWIW, not in my experience, but I can't say it wouldn't happen.
Countries
The heaviest caveats apply here
Italy: Quite a long established African presence. I've seen prejudice for sure, most notably in the North of the country, where their distrust of migrants from the south of Italy shifted to a distrust of migrants from overseas. Difficult to judge how prevalent it is, and whether a tourist would experience it.
Portugal: Perhaps my recommendation, as there appeared to be a Brazilian style racial integration on my one holiday there. The food and wine is superb IMO (and it can be great value as well).
Spain: I've not visited, so my only perspective is from the news, which does rather seem to paint Spain as having some of the worst residual prejudice. I have no idea how true that is in real life.
France: Long time integration, though the news does have occasional blow-ups of racial tension.
I can't give any insight into Turkey or Greece. Both have tourism as significant industries.