Brown chick hatched out of pure BBS ameraucana egg?

[Alliegeiger]

So I have a flock of mostly BBS Ameraucana. My single roo is a very handsome blue Am. but we had culled an olive egger rooster 2 weeks prior to me collecting the eggs I incubated.
Was I wrong in assuming two weeks was long enough to get his genes out of the mix?
All of my BBS eggs hatched looking like pure ameraucanas except for this little one. Is it safe to say this one is a definite Easter Egger?
And Can I be safe in assuming the others that are grey are pure? Would they definitely have different colouring if it was the olive egger that was the dad?

 

[sourland]

Hens can retain sperm for 2 weeks with high fertility, 3 weeks with moderate fertility, and sometimes some fertility up to 4 weeks after removal of a rooster. The 'chipmunk' chick is a crossbred. The other chicks may or may not be pure Ameraucanas.

 

[Alliegeiger]

Hens can retain for 2 weeks with high fertility, 3 weeks with moderate fertility, and sometimes some fertility up to 4 weeks after removal of a rooster. The 'chipmunk' chick is a crossbred. The other chicks may or may not be pure Ameraucanas.

Thankyou for your quick response. I shouldnt have jumped the gun but I was so excited to use my new incubator lol! Oh well.
What are your thoughts on all my pure looking ones. Can I safely assume they are pure because of their grey colouring? Are all Easter Egger chicks shades of chipmunk?

 

[The Moonshiner]

No not all EEs are chipmunk pattern.
No you can not assume the others are ameraucana.
BBS ameraucana are extended black. Extended black is dominate to most everything. When crossed with most patterns the chicks are born black.
Any or all the grey chicks could easily be from the other rooster.
Honestly I'm quite surprised you hatched a chipmunk striped chick from a pure BBS hen no matter what the rooster was.
I'd be questioning the purity of the hens or at least the BBS purity of them if it was me.