Green is by far the most luminous color in the visible spectrum with dark purple being the least luminous. Plants that reflect purple absorb the most visible light and can produce the most sugars. Most plants must undergo a chemical transition to shift from production to dark mode and by choosing to reflect green maximum energy production is sacrificed for internal chemical stability.
What does luminous mean exactly in this context?
I know that our eyes are most sensitive to green. For example a green LED needs less power to seem as bright as a red LED.
But our eyes don't matter in this subject. So I am scratching my head about what you mean that green is the most luminous color?
I suspect luminosity to mean percentage of brightness for a given frequency from a total light source assuming white light. For a more precise definition I would look to physics.
The fact that our eyes are most sensitive to green is probably not an accident, but is it due to the color of leaves, or is it due to sunlight?