Purple sprouting

A friend had some chitted potatoes spare – a variety I’ve not grown before.
They took their time appearing, then amazed me with the colour of their first leaves!
They aren’t planted in a lawn; it’s just that I am enthusuastic
about lawn clipping mulches, which both feed the soil
and suppress weeds between rows very well.
Alas, the variety name is very much out of favour at the moment –
to give you a naval clue,
The battleship bearing the same royal title had the pennant number 19.