[Redcloak]

But that doesn't make any sense. If plant A is over here absorbing light between 600 and 700 nm, plant B in some other location, also absorbing light in that band, isn't affected at all. They don't compete. The plants that used retinal didn't suck up all the light in that particular spectrum.

Plants compete for light by growing taller and getting out of shade cast by other plants. Being short, but using a different spectrum of light doesn't help a plant; it's still in the dark.

[49th]

However, when both types of plants are located in the same area, and lets say that this area it does make sense for one type of plant to absorb a different section of the spectrum. Growing taller isn’t the only way that plants compete with each other for light, it’s merely the most readily apparent.

[antiRepublicrat]

Plants compete for light by growing taller and getting out of shade cast by other plants. Being short, but using a different spectrum of light doesn't help a plant; it's still in the dark.

I think the idea here is that the microbes were everywhere, coating most things, and blocked only green light from going through. I don't think they have any real evidence for this, but it seems plausible to me. Interesting idea.