>All three receptors fire. However, the green receptor has much better sensitivity than the red receptor, so violet triggers the strongest response in blue and red.

I'm confused - it sounds like you're saying it's so off-peak for all of them that, even though it's more proximal to blue, it is effectively equally out-of-range for all three - except that the green receptor is more sensitive. But then that would mean it should look more green, rather than more red and blue, no?