Columbian breeds can be based on eb/eb(brown) e+/e+(wildtype) eWh/eWh(wheaten) ey/ey(recessive wheaten) due to the melanizing effect of ER/ER(Birchen) and E/E(extended Black) thy cant be used as based....
the rest of their genome is Co/Co(Columbian, Restrictor) S/S(Sex Linked Dominant Silver) and the rest of their genome remaining wiltype in nature(like bl+, b+, db+, mh+ and so forth) you should try to avoid crossing Red enhanced birds with them(gold s+ and/or mahogany) becuase this down the line will produce Rusty males that will show some straw coloring on the hackle, so if doing an outcross it is best to use Silver birds that lack red enhancers
the rest of their genome is Co/Co(Columbian, Restrictor) S/S(Sex Linked Dominant Silver) and the rest of their genome remaining wiltype in nature(like bl+, b+, db+, mh+ and so forth) you should try to avoid crossing Red enhanced birds with them(gold s+ and/or mahogany) becuase this down the line will produce Rusty males that will show some straw coloring on the hackle, so if doing an outcross it is best to use Silver birds that lack red enhancers