I am using the one with 'strong' marked on the bottle, so I guess that's the green one, but it doesn't taste that way. And further, you have to be a little creative with your taste buds to guess that it's even a blue cheese!
But to be honest, I have felt that with all the blues I have made (excpt for the stiltons which have the flavour but not the blue look). I know the recipe says to use 7 drops (as I recall), and I use a lot more than that, but still can't get the flavour to get even close to that in the shop varieties. I made another blue vein yesterday, so hopefully there'll be a better outcome with this one.