I wonder if he’s related to Penny. Her lab relatives on Embark are all labs, and most of them are silver (generally why they get tested since it’s pretty unusual yet)
Could be a chocolate lab. Some of the chocolates come out in a silvery color. The aficionados have been lobbying to have them recognized as a distinct fourth color of lab separate from the chocolate ones.
There’s a line of labs that have the same dilute gene as weims and it turns the same silver on chocolate like theirs. Guy that started selling them swears up and down it wasn’t introduced via weims but most people think that’s bs.