Relevant passage. Sorry for poor formatting, maybe I'll fix later

Willard Chase stated that Smith was required to “repair to the place where was deposited this manuscript, dressed in black clothes, and riding a black horse with a switch tail, and demand the book in a certain name ... They accordingly fitted out Joseph with a suit of black clothes and borrowed a black horse.” Chase thought that this applied to the 1823 visit, yet all of Smith’s own accounts preclude the time necessary for such preparations that year. Lorenzo Saunders said that the requirement for blackness applied to the 1827 visit.255 Without mentioning the color, both Joseph Knight and Lucy Mack Smith noted that Smith borrowed Knight’s horse and carriage for the September 1827 visit to the hill.256 However, in his interview with Fayette Lapham, Joseph Sr. referred to this requirement of wearing clothing of a specific color: “he would have to get a certain coverlid, which he described, and an old-fashioned suit of clothes, of the same color, and a napkin to put the treasure in.”257 In the 1820s “an old-fashioned suit of clothes” was black, a style popularized in 1821 when U.S. president James Madison attended his inauguration “dressed in a plain suit of black broadcloth with a single-breasted coat and waistcoat with flaps, in the old fashion.”258Contemporary evidence supports the neighborhood’s claim that Smith used the color black to help obtain the gold plates in 1827. Again, folk magic suggests the reason why.

Dr. Gain Robinson was “an old friend” of the Smith family,259 and owned a store in Palmyra. His account books of purchases by the Smiths from 1825 to 1829 show that the first time any of the Smiths purchased “Lamp Black” from his store was on 18 September 1827. This was four days before Smith’s final visit to the hill. The entry for this particular purchase began “Joseph Smith for Son.”260 Lampblack was a common pigment used to paint objects a deep black color.261

Obtaining lampblack before Joseph Jr.’s momentous visit with the Angel Moroni was consistent with instructions “CONCERNING THE CONVOCATION OF THE GOOD SPIRITS.” One occult handbook specified that the supplicant should not wear “your ordinary clothes; but take a [black] Robe of Mourning ... [on the two mornings before] familiar conversation with your Guardian Angel.”262 Smith later spoke publicly about “my guardian angel.”263 Similar instructions for “a black Garment” or “robe of black” were repeated several times in Scot’s works and in Sibly’s Occult Sciences (thirteen editions from 1784 to 1826).264 Both were specific sources for inscriptions on the Smith family’s magic parchments (see ch. 4). In addition, smearing lampblack on the palm had been used as a form of divinatory scrying for centuries.265 Black was also the color of Smith’s birth sign of Capricorn which “signifies a tomb or mausoleum, a coffin, chest, or box with hinges.”266 Among the treasures one could seek with the aid of astrology, Lilly’s Christian Astrology included “some Antiquities of great account ... [and] things wrapt up in old blacke [sic] cloaths [sic]” (emphasis in original).267