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)