Back 2 Nephi 5, in God cursed the Lamanites, causing "a skin of blackness to come upon them" to make them appear repulsive to the "white, and exceedingly fair and delightsome" Nephites.
And it worked, too. The Nephites hated the Lamanites "because of their filthiness" and dark skins. But God says that the filthy Lamanites are more righteous than the Nephites, because they haven't committed whoredoms by having more than one wife like the Nephites (and Joseph Smith, Brigham Young, and Mitt Romney's great grandfather).
The Lamanites ... whom ye hate because of their filthiness and the cursing which hath come upon their skins, are more righteous than you; for they have not forgotten the commandment of the Lord, which was given unto our father -- that they should have save it were one wife, and concubines they should have none, and there should not be whoredoms committed among them. Jacob 3:5God warns the Nephites that unless they repent, he will make their skin even darker than that of the Lamanites.
Unless ye shall repent of your sins that their skins will be whiter than yours. Jacob 3:8After delivering God's dark-skin warning, Jacob spoke about many more things, only 1 percent of which he included in his small plates. But you can read all about them in the larger plates.
I, Jacob, spake many more things ... And a hundredth part of the proceedings of this people, which now began to be numerous, cannot be written upon these plates; but many of their proceedings are written upon the larger plates. Jacob 12-13Jacob's small plates are called the plates of Jacob, which were somehow made by the hand of Nephi after Nephi died.
These plates are called the plates of Jacob, and they were made by the hand of Nephi. Jacob 3:14And that's all Jacob has to say about that.
And I make an end of speaking these words. Jacob 3:14b