The riddler invites the candidate to cover his left eye, and stare at a red piece of cloth; then cover the right eye, and stare at the grass. After such an exercise, most people report that the grass looks greener through the left eye than through the right. One eye becomes slightly and temporarily desensitized to green.
Q: "Who is the Master (or 'god') who makes the grass (or 'leaves') green?"
A: "I AM"
There's a popular adage that claims "the grass is always greener on the other side
". In Paradise Lost
, Milton notes that "the mind is its own place, and in itself, can make a Hell of Heaven or a Heaven of Hell". The Illuminate knows that perception is key to satisfaction, and mastery entails some engineering of one's own perceptions.
(A tip of the thinking cap to Robert Anton Wilson
for reminding me of this Zen
-like riddle, in Reality Is What You Can Get Away With