thank you! I will take a picture of Sambo tonight from a couple of angles and in the sun.No, he's considered White. He definitely had other color genes since white just 'covers them up', but he was white. One of the original parents were white, and white is recessive, so all the ducklings you got from those parents were split to white. Then you bred them together, and of course a white duckling was produced - your drake, which you lost. All your birds from the original pair are split to white and could still produce whites if they were bred to a white bird or a bird carrying white.
Do you have a current picture of him? I vaguely remember awhile ago we were questioning if he was chocolate or black. When he first molts, do the new feathers come in brown, or black? I'm thinking he may be a black that is just sun bleaching brown. A real chocolate would be chocolate all the time.
The white on the chest is Bibbing. It's a dominant gene, linked to Extended Black. If you breed a duck that's on the black base, bibbing comes along with it. You can remove this bibbing by adding the Dusky gene, which is how you can get solid black/blue/chocolate etc birds without the bibbing.
Pied is caused by the Runner gene which, as you would imagine, is named after Runners and their Fawn and White coloration. Pied is white markings places other than the chest. It's what causes the white markings in Fawn and White color, it's what causes the white patterning in Magpie, it's what causes the white in Ancona color, etc.