"Thus in Jamaica once upon a time
(Ah, well remembered by the man of rhyme!)
Quako, high priest of all the negro nation,
And full of negro faith in conjuration,
Loaded his jackass deep with wonder-bags
Of monkey's teeth, glass, horse-hair and red rags..."
This 18th century poem attributed to "Peter Pindar" seems to be accurate in its description of mojo bag contents of the era (at least as far as the glass, horse-hair and rags... I have not seen monkey's teeth mentioned otherwise in historical sources, but that may be due to the rarity of monkeys in America.)
While there is tradition nowadays of making the bag itself of red cloth, in older sources red cloth is actually most commonly utilized inside the bag as an ingredient all its own. In African belief, red was reportedly thought to be the favorite color of spirits; additionally, if the bag was for harmful intent (as Quako's is) red contents were perceived to be particularly powerful and desirable. Red clover, red berries of Jack-in-the-pulpit and all kinds of red-colored things were all historically used in evil intentioned trick bags based on their color.
Mojo is a word that older scholarship holds to derive from the word moco, from Gullah. New scholarship says, however, that it comes from Kongo mooyo.
Moco means magic. Mooyo means a spirit or nkisi. Which do you think is the better description?