Greenery of Vegetation in Nature

It's great fun observing Nature and to try and learn Her ways in establishing  equilibrium amongst the living/ nonliving entities of Her creation. 

It was the first time that this phenomenon of GREENERY of the entire plant family struck me (not from an aesthetic angle which I'd enjoyed  all my life like most and felt grateful to Nature) but the 'WHY?' and 'HOW?' of it.

Why are the leaves of most trees and plants green?

Biologists will tell us that green colour signals the presence of 'chlorophyll ' which helps the trees/ plants DIGEST their food with the help of sunlight and also in the process absorb carbon dioxide from atmosphere and produce carbohydrates for its growth  and in return exhale fresh oxygen into the atmosphere and let other life forms to get their share of oxygen and thrive. A wonderful way of promoting most of animal LIFE which craves for oxygen.

My enquiry is different.

Green colour means that the leaves THROW AWAY the GREEN of the VIBGYOR set of colours of the sunlight. The rest of the colours are absorbed by the leaves. Why do the leaves choose to discard particularly green colour. Why not any other colour? (There are of course rarely some plants which do that )....I simply have no answer.

Look at the process of a leaf aging and ultimately falling off. When it is formed it is tender and light Violet in colour, then it turns Indigo. We don't practically see Blue colour, it almost skips Blue stage or perhaps briefly skims over it to become Green and stays so for a long time, maybe months, then turns Yellow, stays so for some time, then Orange, then turns Red in some trees ( the last two phases more explicit in, perhaps,  cold climes/ higher latitudes) or turns Brown (before falling off, particularly in hot climes) which is a combination of Green, Yellow, Orange and Red. So the colours that the foliage throws away is progressively VIBGYOR !!! Why in that order which is precisely that of the colours in sunlight...What do the leaves/plants/trees benefit in the whole process?.... I've no answer.

Why do the leaves choose different durations to discard the various colours with maximum time for Green. Are the durations as a percentage of the entire life span of a leaf characteristic of the specific category of the tree?... I do not know.

 Nor do I see an answer in the literature.