Again, different cameras, different lighting, different backgrounds make the same color look different in different photos. Seibertron's pics are the most likely to be color-accurate because he's got a TON of experience with photographing Transformers. TFU's photos are of much lesser quality.
I think there's only one version of this figure. It has two shades of green - a bright green and a brownish green - and the brownish green parts appear more brown or more green depending on the lighting conditions and the photo (as well as your monitor).
I see. Many thanks for the answer! it just incredible and interesting to know that of all BW figures I've ever known, Alligator Megatron's colors just seem to be from green to brown depending on how it the picture was taken. This is something (from experience) I do not seem to observe with other figures of the line. No matter how the pictures are taken, I always see them in their usual colors.