"14 And it came to pass that those Lamanites (people of color) who had united with the Nephites (Mormons) were numbered among the Nephites;
15 And their curse was taken from them, and their skin became white like unto the Nephites;
16 And their young men and their daughters became exceedingly fair, and they were numbered among the Nephites, and were called Nephites. And thus ended the thirteenth year."
-- III Nephi 2:14-16 (Book of Mormon)
This fictional tale takes place during the time of the first century AD. Remember that there are no historical data or archaeological data that proves that Lamanites and Nephites even existed upon this earth.
These verses stated that some of the Lamanites turned away from their wicked ways. As a result, their skin color turned from dark to white. These verses are implying that anyone that has dark skin pigmentation is cursed. That is horrible, LDS! Skin color doesn't determine how much goodness a person has within his or her heart.