Better question is, “Why do we perceive leaves as green?”
OK, this seems like an obvious question. “Duh, because of chlorophyll, dumbass!”.
But I was sitting around with a bunch of Real Actual Scientists, and we managed to stump one another. Do leaves transmit green light? Absorb it? Reflect it? Fluoresce? What? What do our eyes actually detect? Anyone know offhand? We came up with a lot of conjectures, playing the old “I can top that idea” along with the “I can argue this for HOURS” game. But seriously, anyone know the actual answer or process?
To put it simply (and inaccurately)… sunlight is multicolored; the leaves absorb everything but green light, green light is reflected, that’s what we see.
To expand on GHO57’s answer, chlorophyll absorbs light most strongly at the blue/purple end of the spectrum, with a smaller absorption peak in the orange region.
If you subtract those orange, blue and purple wavelengths from white light, you are left with mostly green, as you can see from the spectrum. So when sunlight bounces off (or passes through) leaves, they appear green.
Same with any coloured object, really - with the exception of things that actually emit their own light, objects are a particular colour because they reflect that colour while absorbing other colours in the spectrum.
No one with a Smartphone among ya, to google the question? Just curious, since it sounds like a lively time, but no real answer until you’ve posted on the SDMB, I take it, long after the group went their separate ways.
Interestingly, IIRC the human eye can distinguish more shades of green than any other color, which makes sense from an evolutionary perspective as distinguishing plants from each other would be a big deal for early man.
Out of curiousity, just what type of science do these real actual scientists do? I think that for most people in the sciences, the concept of apparent color of an item and its relationship to light absorbtion/reflection is fairly well known and understood.
Are you sure that has anything to do with plant life and not just the fact that green’s in the middle of the spectrum? There’s a lot of overlap in the sensitivity of the three different photopsinsin the green region. I blame that.
ETA: Here’s a rough sketch of chlorophyll’s absorption spectrum.
How could your eyes perceive leaves as being green unless the leaves reflected that colour into your eye, or more accurately unless that leaf preferentially absorbed all other spectra? How could any “Real Actual Scientist” think a leaf could absorb green light, yet your eyes see it as green? To put it yet another way, what exact kind of green leaf were they smoking at the time?