The Green Cross is a well-known international environmental/peace group. Check out their website:
http://www.greencrossinternational.net/ ... index.html
Maybe Neopets wanted to show support of that group rather than the Red Cross, which, if I recall correctly, botched up the 9-11 contributions.
And, I am in the US--I have green crosses, McD's and Cereal Adventures. Maybe the green crosses will counteract the ill-effects from all of those happy meals and bowls of cereal!