And on a more serious note (if there can be one here) the color yellow makes WAY more sense than wood.
As most of the lantern power comes out in the form of a green light, they may be vulnerable to a specific frequency...which just happens to be from the spectrum of yellow.
But Alan Scott power source is entirely magical in nature and has nothing to do with the green energy source. Even the lanterns who are vulnerable to the yellow energy can now overcome that limitation. Scotts' ring is the collection of magical energy for an entire universe distilled into a single stone.
So obviously that stone is vulnerable to wood? Not plants, or living matter, wood. Hacksaw Jim Duggan could beat this guys ass.[/QUOTE]
Well technically it is that magical power manifesting as a green flame that can be shaped. There is a kind of narrative irony that his flame based power is useless against wood. That said, how the frick often does it really come up? Even a dude coming at him with a bat has to get close first. The weakness to wood really doesn't come up much, plus he spends like all his time with the JSA. So Wildcat and Atom Smasher can beat up on Blackbriar thorn while GL takes out the rest of the Injustice Society single handed.