To clarify - for gulastra, you would expect the light hair in the tail to be white or grey rather than cream or tan if that makes sense? The tone is just too warm IMO.
As far as silver goes, you would expect to see some sort of dilution to the black points of the horse, such as the legs. These are such a clear black, while a silver tends to have almost a dusty look to their legs.
Smrobs I don't believe that there is any tested silver, no. However, only a few years ago there were no tested silver QHs either. Silver tends to be one of those colours that people don't recognise - they just see sunfading in a minimal and chestnut with flaxen or a black palomino in max. Add into the mix that it doesn't display on red, and you can potentially have generations go by without silver expressing, and then you have a 'random' weird foal, you wouldn't even think was silver until you tested.