If memory serves me correctly here, there is a syndrome called 'Synothesia'. If I have time I'll try to look up the precise term later today. Loosely concept is that the hard-wiring in the brain is different to the normal brain structure and that the senses are perceived in a confused, but interesting fashion.
For instance, someone with the syndrome may perceive sounds or odours as colour. Or they may represent numerals as colours in terms of normal thought processes. It isn't necessarily a bad thing, and is largely down to how cognition develops in the foetus and young infant. Past a certain age, perhaps, around 7 or so, the brain's neural development or hard wiring is almost fixed permanently, after which time it becomes less and less pliable. So, theoretically, everyone has the capability to experience synothesia, but it is an exceptionally rare but, nevertheless medically documented condition and encountered by psychologists.
The one strange thing you've described is that only green is seen, a limiting condition, whereas usually the condition extends an individual's cognition well beyond the human norm. Hope that is of some help to you.