Understand. The results I got from the Buff male X Buff Columbian crossed to Silver Columbian were exactly as I expected and as you said, sex-linked. Good to know that the females cannot carry the silver and gold at the same time. So that discards my theory about why the f1's looked the way they did.
The Buff Columbian in the 3rd photo is 2nd generation removed from the Buff Male/Buff Columbian crossed to Silver Columbian, so if she's carrying Mottling, it's not something I've intentionally put in there. I wing band every one of my chicks so I am pretty sure I haven't misrecorded lineage, plus I get a couple that look like her every year, so there must be some recessive Mottled in there somewhere.
As far as down color goes, to clarify...Dark buff with gray back. Very similar to Silver Columbian but replace the yellow down with a brownish buff down.