I finally got my hands on a Japanese Painted fern AKA Athyrium niponicum var. pictum. The label says 'Metallic' so that may be this variety but can also be a synonym of pictum. It should look very good on the fern stand with the other ferns. I hope it will do okay in the container.
The stem is a nice purple and the leaf themselves both green and a shiny white/grey. I am curious to see whether the colour will change with more or less sun. Where it is now it does get a couple hours of late evening sun even though it is shaded slightly by the tree ferns.