Well if you go by definition as APA SOP it is-
Buff:
A medium shade of Orange-Yellow color with a rich golden cast; not so intense as to show a Reddish cast, nor so pale to appear Lemon or light Yellow. The term is generally used in refering to the plumage color of all Standard "Buff" varieties of poultry.
American Standard of Perfection
2001
I was told one time by a poultry judge the the "ideal" buff color would be the same shade as a good gold watch.
Chris
Buff:
A medium shade of Orange-Yellow color with a rich golden cast; not so intense as to show a Reddish cast, nor so pale to appear Lemon or light Yellow. The term is generally used in refering to the plumage color of all Standard "Buff" varieties of poultry.
American Standard of Perfection

I was told one time by a poultry judge the the "ideal" buff color would be the same shade as a good gold watch.
Chris