Paul Foster Case

American occultist, one-time member of the Alpha et Omega, founder of the Builders of the Adytum (B.O.T.A.), which taught the system by correspondence course to a mass American audience and still does.

His innovation was pedagogical and genuinely good: students were sent an uncoloured deck and told to paint it themselves from the colour scales. You learn the correspondences by putting them on with a brush.