Having written "I believe..." as the introduction to my response above, I decided that I really needed to look further into this matter. The fact is that I
have believed just that for many years, but have no idea where I originally got the notion
from.
If you click
here, the link will take you to a website and, once there, if you scroll down to about the middle of the page, you will see a sentence which reads, "Unsurprisingly, it is printed on pale green paper."
I have no idea how authoritative that site is, but it certainly seems that there is someone
else who - like
SeaJayPea above - believes the actual paper itself is green.
Perhaps you can do some Googling yourself,
5freemen...I'd certainly like to get the answer absolutely definitively. Cheers