well, those particular stones are modern representations of what they think might have been...
This is all at the CAIRN (Centre Archéologique d'Initiation et de Recherche sur le Néolithique) centre in Vendée, which is not only a museum with the usual displays of things and exhibitions, but is a research and learning centre.
The stones have been painted with what they think might be real neolithic paints and designs, with the paints based on the same sort of thing as the ancient cave paintings are.
I am sure they didn't just make it all up.