The attached pics are from the VT Series II sales brochure, it shows there were only 3 colours for the SS in Series II, Heron, Bermuda, and Tiger, I have circled them on the colour chart, I can't recall seeing a VT Series 1 in Silver either.
And that is one of the cars I googled when I said yes. When ordering a new car I think you can choose a different colour, so that might explain the silver VT SS's I saw.
That's interesting - normally I'd assume an SS in a non-SS colour is an Exec V8 with an SS bodykit on it, but that particular car doesn't show any obvious signs of being fake. From time to time Holden does produce small batches of cars in test colours etc so I wonder if that was part of a batch to test how a silver SS might look ahead of the VX? I notice it's a 2000 build so that adds a bit more weight to that theory.
Could also be that Holden offered silver very late in the VT's life - IIRC the VN SS, for example, was not offered in white until some time in 1991, not long before the VP release.