Kate,
Several of my 'Silverine' open pollinated seedlings had that shade, including the one I named 'Silver Song', which was probably a self pollination. SAs it matured it became a solid silver. I self pollinated some 'Silver Song' last season but only got a handful of seedlings. In this case I wqas trying to get an even broader-leaved version. That waterlily form is so nice I wouldn't mind a whole color range with that form.
Kevin