The "leaf color" argument aggravates me, too. Some plants just don't have the "proper" yellowish-green color no matter how much light you give them. And that doesn't mean that the light is insufficient - it just means that the plant has darker foliage. I swear I have a certain Catt. that would stay olive green if I bathed it in lava. I have a couple of others that do have that light green tint, and they're all grown in the same environment.