Church manual quotes Spencer W. Kimball on interracial marriage.
Eternal Marriage Student Manual: Religion 234 and 235 (Salt Lake City: The Church of Jesus Christ of Latter-day Saints, 2003), 169, 188
We are grateful that this one survey reveals that about 90 percent of the temple marriages hold fast. Because of this, we recommend that people marry those who are of the same racial background generally, and of somewhat the same economic and social and educational background (some of those are not an absolute necessity, but preferred), and above all, the same religious background, without question. In spite of the most favorable matings, the evil one still takes a monumental toll and is the cause for many broken homes and frustrated lives.
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“. . . We recommend that people marry those who are of . . . somewhat the same economic and social and educational background (some of those are not an absolute necessity, but preferred), and above all, the same religious background, without question” (“Marriage and Divorce,” 142–44).
It is worth noting that the second quotation removes the portion about "racial background."