According to Alexandre Tokovinine of Harvard University,
...the significance of the logogram for the color black extends beyond the notion of color into a broader range of meanings that includes hollow objects … The association of the term ihk with the notion of emptiness is indicated by the presence of dark or cross hatched spots on representations of objects, which are not necessarily black, but almost certainly hollow.This opens up some interesting possibilities. “Emptiness” could of course mean "emptiness of soul." We might expect they were excommunicated from the Church and assumed different habits and practices. 2 Ne 5:24 tells us that because of the curse "they did become an idle people, full of mischief and subtlety and did seek in the wilderness for beasts of prey." The reference to "beasts of prey" could mean the jaguar in a Mesoamerican context - a beast of prey which was worshipped.
In the context of skin, perhaps there was a lack of clothing? Or garments? As far as literal darkness goes, lack of clothing would certainly cause darker skin under the hot Mesoamerican sun. Interesting possibilities.
Tokovinine goes on to state that when Mayans described objects and beings as a certain color, they usually didn’t mean the object or being actually was the color: "Classic Maya narratives’ fascination with extensional meanings … cautions us against automatically linking every instance of basic color terms in writing and imagery with color properties of objects or beings. The actual evidence suggests that, more often than not, this was not the case."
All of this is consistent with the fact that Joseph Smith changed the word “white” to “pure” (2 Nephi 30:6) in the 1840 edition of the Book of Mormon, before race was an issue. Nephi may have written a word for the color “white,” intending to convey a meaning other than color, but which in English is usually understood as just a reference to the color. Of course, Nephi would have expected his people to understand in terms of their culture, not ours, and that would be true regardless which language Nephi was writing in. Every language, not just Mayan, has a word for black. Presumably it is the color, not the language, which is the underlying factor behind the extensional meanings.
This explanation is also consistent with the Book of Mormon telling us the mark on the wicked is something they do to their own selves (Alma 3:18-19).
And, of course, the Native skin color of people living in the Americas when Nephi arrived was probably a beautiful brown or dark brown, having nothing to do with the mark the wicked placed on themselves.
In response to this, some people may quote Spencer W. Kimball or other church leaders and point out how they evidently understood the word "blackness" in terms of more modern cultural assumptions. If they had ideas that did not bear out, that does not diminish their stature as Apostles. I think we can learn a lot about how revelation works by looking at Christ's mortal ministry. He didn't reveal everything to His Apostles, and they had some misconceptions, but He was still leading them.
As knowledge shines forth in the Last Days, the Lord lights my path of faith with His Spirit.