There is no American standard yet, but here's the draft that the Marans club is proposing:
Draft Color Standard for Brown Red Marans (Black Copper)
Disqualifications
White in ear-lobes. Two or more white feathers in plumage.
Color of Male
Comb, Face, Wattles and Ear-Lobes: Bright red.
Beak: Dark Horn.
Eyes: Reddish bay.
Shanks and Toes: Dark Slate, bottom of feet pinkish white.
Head: Lustrous deep orange.
Neck: HackleLustrous deep orange with narrow dark stripe through the middle of each feather terminating in a point near its lower extremity. Front of neckBlack with narrow lacing of deep orange.
Back: BackLustrous deep orange. Saddlesame as hackle.
Tail: Main TailBlack with slight luster, Sickles and CovertsLustrous beetle green black.
Wings: Shoulders and FrontsBlack. BowsLustrous deep orange to match back.
CovertsLustrous black.
PrimariesBlack.
SecondariesBlack, with exposed portion forming wing bay, with slight luster.
Breast: Upper breast, black with narrow lacing of deep orange. Lower breastblack.
Body and Stern: Black.
Legs: Lower ThighsBlack
Shanks and ToesBlack.