Doing this will result in only max. 25% Olive Eggers as the parents already bring 100 % brown from the BCM and only about 50% blue/green from the EE hens.
Pairing this offspring again to BCM leads to 75% BCM genetics and about 25 % EE genetics, but there even is the risk of some other non...
With EEs you never really know about their ancestry/genetics, so using a male whose parents both were blue/green eggers would bring better results.
Crossing cream colour eggers with a BCM rooster will usually just result in their offspring's eggs to be several shades of brown instead of olive...