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Pergunta: Será que alguns líderes da Igreja acreditavam que a pele dos lamanitas iria virar branco?
Question: Did some Church leaders believe that the skin of the Lamanites would turn white?
Some Church leaders, most notably Spencer W. Kimball, made statements indicating that they believed that the Indians were becoming "white and delightsome"
Once such statement made by Elder Kimball in the October 1960 General Conference, 15 years before he became president of the Church:
I saw a striking contrast in the progress of the Indian people today ... they are fast becoming a white and delightsome people.... For years they have been growing delightsome, and they are now becoming white and delightsome, as they were promised.... The children in the home placement program in Utah are often lighter than their brothers and sisters in the hogans on the reservation. 
President Kimball felt that the Indians were becoming a “white and delightsome” people through the power of God as a result their acceptance of the Gospel. This was not an uncommon belief at the time. At the time that this statement was made by Elder Kimball, the Book of Mormon did indeed say "white and delightsome." This passage is often quoted relative to the lifting of the curse since the phrase "white and delightsome" was changed to "pure and delightsome" in the 1840 (and again in the 1981) editions of the Book of Mormon. The edit made by Joseph Smith in 1840 in which this phrase was changed to "pure and delightsome" had been omitted from subsequent editions, which were actually based upon the 1837 edition rather than the 1840 edition. The modification was not restored again until the 1981 edition with the following explanation:
Some minor errors in the text have been perpetuated in past editions of the Book of Mormon. This edition contains corrections that seem appropriate to bring the material into conformity with prepublication manuscripts and early editions edited by the Prophet Joseph Smith.
Is the lifting of the curse associated with a change in skin color?
The Lamanites are promised that if they return to Christ, that "the scales of darkness shall begin to fall from their eyes:"
And the gospel of Jesus Christ shall be declared among them; wherefore, they shall be restored unto the knowledge of their fathers, and also to the knowledge of Jesus Christ, which was had among their fathers.
And then shall they rejoice; for they shall know that it is a blessing unto them from the hand of God; and their scales of darkness shall begin to fall from their eyes; and many generations shall not pass away among them, save they shall be a pure and a delightsome people.2 Nephi 30:5-6
The Book of Mormon indicates that the lifting of the curse of the Lamanites was the removal of the "scales of darkness" from their eyes
It seems evident from the passage in 2 Nephi that the lifting of the curse of the Lamanites was the removal of the "scales of darkness" from their eyes. It is sometimes indicated that Lamanites who had converted to the Gospel and thus had the curse lifted also had the mark removed. If the mark was more in the eyes of the Nephites than in a physical thing like actual skin color, its removal is even more easily understood.
And their curse was taken from them, and their skin became white like unto the Nephites; 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. 3 Nephi 2:15-16
As with the invocation of the curse followed by the application of the mark, this passage indicates that the curse was revoked and the mark was removed when the Lamanites' skin "became white like unto the Nephites." The Book of Mormon makes no mention of any change in skin color as the result of the conversion of Helaman's 2000 warriors, yet these Lamanites and their parents had committed themselves to the Lord, and were often more righteous than the Nephites were.
Thus, although a change in skin color is sometimes mentioned in conjunction with the lifting of the curse, it does not appear to always have been the case. And, as discussed above, it may well be that Nephite ideas about skin were more symbolic or rhetorical than literal/racial. This perspective harmonizes all the textual data, and explains some things (like the native Lamanite and his band of Nephite troops deceiving the Lamanites) that a literal view of the skin color mark does not.
Leaders were probably unaware of a change made by Joseph Smith to the first edition text
Joseph Smith altered the phrase "white and delightsome" (in 2 Nephi 30:6) to "pure and delightsome" in the second edition of the Book of Mormon. This change was lost to LDS readers until the 1981 edition of the scriptures. It may, however, demonstrate that Joseph Smith intended the translation to refer to spiritual state, not literal skin color per se.
- Spencer W. Kimball, General Conference Report, October, 1960