I have heard the debate on the correct colour for Buckeyes and I have seen many shades and interpretations of "mahogany bay". I think Buckeye breeders, if in doubt as to exactly what they should breed for, should go back to what the creator of the breed stipulated and use her words as a guide:
"As for color—well, my own are so dark a red that at a little distance in the shadow they look fairly black, but when the sun strikes them and brings out that rich, garnish luster…with the very darkest of red plumage, hens containing some black not being objectionable to me as long as the males kept that dark red shade I admire.”
As for under colour, again, the creator of the breed stipulated that they should have under colour:
"My reason told me that all wild birds of brilliant plumage had slate, or leaden blue, undercolor, and I felt sure that this dark pigment was necessary in order to retain the dark plumage in the offspring."
Personally I always found the darker coloured Buckeyes much more attractive than the orangey and splotchy ones out there and I'm happy to see more of them out there in breeding programmes and the show rings.