To my knowledge, the existence of "Jam Boys" or "Jamblers" is no more than an urban legend. Depending on where you read, the idea of a Person of Color smothering themselves in Jam and following a white person around changes locations and details from British India, to the American South, to South Africa. There is no historical evidence for it and its also interesting to note that the wiki page for the term was denounced as a hoax.
hi, you may be interested in a similar question (& answer) here