Yes, many Buff Orpingtons have small black feathers/black specks on their body, including in their tail. They might also have small flecks of other color, including white. Its a defect when showing chickens (they are supposed to be pure buff all over), but it won't affect their qualities as a pet or egg layer.
Wow, So I am new to chickens and saw on a this article about mites and seriously got scared. I keep my coop very clean and have not seen any mites on my chickens or around their coop but the 6th photo down looked very similar to their markings which I am now thinking are just spots again. Here is the link to the white feathers that look very much like my buff orpingtons spots. http://boisebackyardchickens.blogspot.com/2011/04/chicken-mites-not-so-glamorous-side-of.html
Hope they are just colorations, made me very nervous since they are known for being around the shoot and that is only where these markings are. (on the tail feathers)
I Thought they might be mite markings. I am new to the chicken world and got my buffs are about 8 weeks old and have started developing these spots. I have also seen a number of websites warning of mites and that they look similar. After seeing this I am positive that my Orpingtons just have new markings not mite residue !!