Not sure what you mean by that, but here's what I know -
Cream crested legbar is an actual breed. When bred within themselves they should always produce blue eggs. Whiting true blue is another breed - they can repopulate themselves, and they lay blue egg. Starlight green eggers and prairie...
She probably is a Starlight green egger. Some of them look just like her. Unfortunately, there's a 15% or so chance that they won't lay green, but will lay tan instead. This happened to one of my SGEs - I had three and one laid tan (others laid green). It also happened to a few of my Prairie...