Yes, Silver Leghorns are silver based, hence why they are called 'silver'. Hens have a black and white penciled, partridge type pattern with a salmon chest. Silver birds are basically white (silver) birds with black patterning.
Think of it this way, all chickens are, genetically, either silver or gold. Black is a 'pattern', not a color gene. There are lots of different genes that control how much black a bird has, and where it can express. Solid white and solid black birds should not be used for making sexlinks because those genes completely hide the base color.
For example, these Easter Egger hens are gold based with black, partridge type patterning. No white (silver) on them at all.
These Barred Rocks are silver based with a black barring pattern.