The way I read this it is a BCM hen bred to Lavender Ameraucana roo and then that hen bred back to a CL roo. I am missing something if that crossing doesn't make green eggs all the time. It would seem there are a lot more blue egg genes in that cross than in the original cross. Kern
When you breed the BCM to a laventar AM, The OE (olive egger) will only have one blue egg shell gene. When bred to the CL, he may not have two blue egg shell genes. There are still some recessive white genes in them sadly. The same is true for AMs. You will sometimes get a blue egg laying CL or AM and they will have a recessive white egg shell gene.
The answer is that the CL rooster must not be double blue! He would need to be removed from breeding.