Or breed the current BCM rooster to hens that lay blue eggs. Depending on how many blue egg genes each hen has, either half of her chicks or all of her chicks will lay eggs in some shade of green.
It sounds like there are several blue-layers to choose from:
If you want to know how many blue egg genes a hen has, there is a genetic test.
https://iqbirdtesting.com/blueegg
Testing a hen may be cheaper than raising several daughters to laying age to see what they produce. It is definitely faster.
You can also test chicks, if you want to only raise the ones that have a blue egg gene. That lets you re-home or butcher the other ones at an early age. You can do this if you buy more olive eggers, or if you hatch chicks from a hen that has only one blue egg gene. If you have a hen with two blue egg genes and a BCM rooster with none, there is no point in testing the genes of any of their chicks, because each will have one blue egg gene from the mother and none from the father.