Pang -
Some flames have a blue part (the 'non-luminous' part) and a yellow
or orange part (the 'luminous' part). This does not mean that the flame
is actually green. A better way to think about it is to imagine that
there are two different flames burning in the same place. If the flame
appears green in spots, it's probably because you're seeing some yellow
flame in front of (or behind) some blue flame and the colors look mixed
together.
-Tamara
(published on 10/22/2007)