You can make stork marks in any color. Just breed two typical grizzles together to make homozygous grizzle (stork mark). They will be mostly white birds with colored flights and tails. In baby feather, they show alot more color and the white tends to moult in with adult plumage.
If the grizzles are ash red, they tend to be more white and pure whites can be bred from them. Still, stork mark is possible even in ash red.
Pied factors and bronze can have effects on them, pieds tend to not show as much color, as would be expected. Bronze tends to show more color, less white.