its a color =]  you can find buff laced birds ect  and not all orps are buff so if someone asks just say you have an orpington.
 
i was given some hatching eggs the other day some will be blue some will be splash and some will be buff (person separated them by color)
 
its kind of like someone walking up to you and telling you they have a red nosed pit bull. red nose isnt a breed its a nose color ask anyone in the show world or tell them that and they will give you this look  (

)  all it is, is a color which is generally seen with that breed of bird like 
mille fleur d'uccle    d'uccle is the breed and can come in other colors such as porcelain or lavender  but it is more common to see mille fleur