The term fair-skinned is common enough that it's very unlikely to be deemed as a politically incorrect term. I did some corpus searches, and found these excerpts, which I think would be fairly safe from being labeled as racist:
The transmission of UVA into the dermis of an untanned fair-skinned individual is approximately 50% of the impinging flux. Even-pigmented persons with brown skin transmit a significant amount of UVA radiation (30-35%).1
Non-melanoma skin cancers occur more frequently than any other type of cancer in fair-skinned populations, and their incidence has been rising rapidly for several decades.2
However, if you were brazen enough to say:
I'm much more likely to do my business dealings with fair-skinned individuals.
then that probably would be considered politically incorrect – but not because you used the word fair instead of light. In fact, if you swapped the word light for fair, I doubt the perceived unfairness of the statement would change.
1(Phillips and Verhasselt, 1994)
2(N.J. Lowe, 1997)
The linguistic processes are technically called Taboo (in this case, Taboo words) and Euphemism, which is substituting a non-taboo word for a taboo word, like saying
intead of
The way it happens is that there are always taboos on certain terms and topics in every culture. These taboo words are the healthiest words in the language, because everybody has to know them, in order to avoid saying them.
(If this sounds crazy, that's because it is -- taboos are unconscious, and not really subject to logic. After all, words by themselves have no powers; it's human culture that produces taboos.)
Anyway, people do need to talk about things, even if it's forbidden, so we substitute "safe" terms (like water closet or crapper or toilet or washroom or men's room or bathroom, instead of "place where one shits in private"). These euphemisms have a short half-life, since once the substitution strategy is detected, the euphemism gradually becomes taboo itself, and is replaced by another euphemism, while the original taboo term goes on forever.
Derogatory, politically (in)correct, profane, vulgar, racist, sexist, and other terms that are applied to language chunks are simply descriptions of the variety of taboo that the terms in question are said to be breaking. They're not categories of words so much as social infractions, which is (luckily) not a matter of grammar.
Best Answer
Depends so heavily on who you're talking to that I doubt any consensus will be reached. I'd guess that this is the kind of issue where maybe 10% of the developed world's English-speaking population cares enough to be deeply and vociferously offended immediately and use your use of the term as an excuse to get in a long, drawn-out argument.
Another 10% would think it's a bit off, but they'd say nothing.
And the other 80% simply would not care.
Would I use the phrase in an official document? No. Partly because it's vernacular. Would I use the phrase in an e-mail to someone I don't know well? Depends on how much I care about whether they might get mad at me. Would I use the phrase in a verbal conversation in person? Certainly, although given how specific the use-case is, I'd still use it infrequently.
At the end of the day it is based on a thing that did happen and that does materially relate to the place being discussed. Like referring to arson as "Detroit Halloween celebrations". Would the people of Detroit like that description? Maybe not. But it's an evidence-based description.