How to differentiate buff orpington chicks for RIR chicks??

[The Birb King]

Is there something that makes it not a buff orpington? I can try and bring it up with the seller.

It is darker and has a spot on the head. Buff orpingtons are supposed to be all yellow

 

[Kearaaaa23]

It is darker and has a spot on the head. Buff orpingtons are supposed to be all yellow

I read that buff orp chicks can have tiny black spots on their head which will feather out to be a darker buff colour? Perhaps this chick is not a high quality buff orp but it is the only one with white feet. It does have a tinge of yellow but not a lot as seen in the pic. The only other one that could very slimly be a buff orp has black striping down its back and orangey feet