The borders of China aren't exactly clear in the image you posted, but here's what I'm seeing:
Europe ranges from 1-14
"Western" ranges from 1-23
China ranges from 12-17
Am I interpreting the image incorrectly? Doesn't it confirm my assertion that China has a smaller range of skin tone?
Edit: The definition of "Western" appears to be very vague, but for reference I referenced at the rough vague shape of the United States to determine the 1-23 figure.
The way I read it almost all of Europe is in the 1-12 range with the exception of Spain. China is 12 to 17 or 12 to 20 depending on how you read the borders. I would eliminate North America from consideration unless we are talking about aboriginals, since it's a melting pot. (That is to say, it goes without saying that it has more variety.)
But my point is only to say that your statement of "greatly reduced range of .. skin color" is a rather exaggerated statement. (For hair color I suppose you might be right ;)
Hard to say due to the lack of precision in the map in the lighter range, but if you think about how incredibly large China is, it stands to reason that your statement might be missing the mark a bit. Especially if you consider other Asian countries. (Which maybe you should, if comparing with "Europe" or "North America"..)
North to south I think it's pretty clear that skin colour goes from light to much darker than Europe.