The color green is almost exclusively used in connection with plants in the Bible, and the meaning is closely connected to the meaning of plants as well. Plants, in general, represent facts, knowledge that we can gather from the world. Green plants are ones that are alive and growing. Since life represents love and goodness, it makes sense that green plants are facts that have the potential for good use. It also indicates that they are the kinds of things we learn through directly through our senses, since to identify green plants we need to actually see the greenness.

(References: Apocalypse Explained 507; Apocalypse Revealed 426; Arcana Coelestia 7691)

7691. 'And they did not allow any green to be left' means the obliteration of every sensory apprehension of truth. This is clear from the meaning of 'not allowing to be left' as obliterating; and from the meaning of 'green' as factual knowledge and sensory evidence, here sensory apprehension of truth, since 'the fruit of the trees' means recognition of good, 7690, and reference is being made to all the green on trees and on the plants of the field. 'Green' means sensory apprehension of truth because truths are meant by 'plant', 'grass', and 'leaf of tree', and from this a sensory apprehension of truth by their greenness. By sensory apprehension is meant the lowest level of perception. A sensory apprehension of truth is also meant by 'green' in Isaiah,

The waters of Nimrim will be desolations, for the reason that the grass has withered away, the plant has been consumed, there is nothing green. Isaiah 15:6.

And in John,

The fifth angel sounded, and out came locusts; and they were told not to harm the grass of the earth, or any green thing. Revelation 9:4.