Pamphlet published by Church in 1974 teaches that the Lamanites were "marked by the Lord with a darker skin."
Lamanites and the Book of Mormon (Salt Lake City: The Church of Jesus Christ of Latter-day Saints, 1974), 2
. . .
After arriving in America, these people planted seeds and harvested crops. They found the earth rich with metals, which they molded into tools for building homes and cities. They built great temples and highways and made beautiful clothes. They had great faith in God and be blessed them, but there were also times of wickedness that resulted in wars and destruction.
Two groups formed and fought each other. One group called themselves Nephites and the other group was known as Lamanites. The Lamanites were marked by the Lord with a darker skin.
The Lamanites were wicked during some periods of history, while at other times they were obedient to God's commandments.
. . .