Exploration brought seven South African Pelargonium species to light that have or may sometimes have zonal leaf markings. They are: Pelargonium zonale, P. alchemilloides, P. inquinans, P. acetosum, P. elongatum, P. ranunculophyllum and P. peltatum. Zonal leaf markings are caused by differential pigmentation due to localized accumulation of particular chemical substances, influenced by genetic and environmental factors.
The soft-stemmed plant in the photo bearing pale flowers with dark purple markings on the broad upper petals is clearly not one of those mentioned. Zonal leaf traits are retained or enhanced in some hybrids or horticultural cultivars.
But the photo is from the veld, from the fynbos near Tulbagh in the Western Cape. The search continues (Manning, 2007; https://www.pacificbulbsociety.org; https://pza.sanbi.org/pelargonium).