The mark of the curse that came upon the Lamanites was that "a skin of blackness" came upon them. A major purpose of this mark was that the Lamanites "might not be enticing" unto the Nephites. (2 Nephi 5:21.) The Lord stated further that the "seed of him that mixeth" with the unrighteous Lamanites "shall be cursed even with the same cursing." (2 Nephi 5:23.)
This is the only reference in the entire Book of Mormon where a definite color adjective is used to refer to this mark. All other references call it, a "skin of darkness" or a "dark skin." It is of interest to note that the terms "blackness" and "darkness" are interchangeable in the Hebrew. Even in modern Hebrew it is not unusual for some skilled translator to render a word black whereas other equally skilled translators select dark as the best translation.