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Buff Columbian Genetics

A buff body, black Columbian markings — and the same Blue locus as everywhere else

Buff Columbian is a buff-bodied bird with black restricted to the hackle, tail and wing tips by the Columbian gene — the same layout as a Light Brahma, just on a buff ground instead of white. Like any black-marked variety, those markings can carry the Blue locus: standard (black), one copy (blue), or two copies (splash) — giving Buff Columbian, Blue Buff Columbian and Splash Buff Columbian. For the wider system, see the Genetics Guide.
Buff Columbian chick with a dark cap over cream-buff down.
Standard Buff Columbian: a dark (black) cap over an otherwise buff chick.
Close-up of buff feathers edged in black at the neck.
Close up, the black sits right at the neck — Columbian restriction, not a wash over the whole body.

The genes that build it

Buff Columbian's base genotype is eb/eb · Co/Co — a brown/buff ground with the Columbian gene clearing black off the body and confining it to the hackle, tail and wing tips:

GeneGenotypeWhat it contributes
Extension — browneb/ebThe buff/gold ground colour, with grey (not white) undercolour.
ColumbianCo/CoRestricts black to the neck, tail and wing tips, keeping the body buff.
Bluebl+/bl+, Bl/bl+ or Bl/BlSets what colour those markings are: black, blue-grey, or splash.1

One locus, three Columbians

This is the same Blue locus story told elsewhere on this site — incomplete dominance, one gene, three looks — except here it is acting only on the small area of black the Columbian gene has confined, not on a solid black bird:

VarietyBlue genotypeMarkings
Buff Columbianbl+/bl+Solid black hackle, tail and wing tips.
Blue Buff ColumbianBl/bl+One copy dilutes the markings to an even blue-grey.
Splash Buff ColumbianBl/BlTwo copies dilute further — pale, flecked markings rather than a solid edge.
Blue Buff Columbian chick with grey-toned markings over a cream-buff back.
Blue Buff Columbian chick: the same buff base, markings diluted to grey instead of black.
Splash Buff Columbian hen with buff plumage flecked pale grey, greyer stippled head.
Splash Buff Columbian hen — two copies of Blue leave the markings pale and flecked rather than solid.
Splash Buff Columbian hen in front of two black-laced-red hens.
The same splash hen (front), alongside black-laced-red flock mates for comparison.
Don't confuse it with Buff White Columbian. "Splash Buff Columbian" and Buff White Columbian ("lemon pyle") can look similar at a glance — both are buff birds with pale markings instead of solid black — but they are built from different genes. Splash Buff Columbian gets its pale markings from two copies of Blue (Bl/Bl), which dilutes black to a flecked blue-grey. Buff White Columbian gets its pale markings from Dominant White (I), which erases black and replaces it with white. Same visual idea — a buff bird with softened markings — from two unrelated loci. Compare them directly with the Compare tool.

Related

You can plan any of these crosses in the Breeding Outcomes tool, or line two of them up in Compare Standards.

References & notes
  1. The Blue locus's incomplete-dominance behaviour (black / blue / splash) is standard Mendelian genetics; see Blue, Splash & Black genetics for the full inheritance table. Extension/Columbian base: Smyth JR Jr (1990) Genetics of plumage, skin and eye pigmentation in chickens, in Crawford RD (ed.) Poultry Breeding and Genetics, Elsevier — see the Genetics Guide references.
Try it: plan a Buff Columbian cross · Buff Mottled · Buff White Columbian