These intensely purple plants lured me over the edge at Nufenen Pass. I wasn't in any danger, but I was the only person down on the ledge below the visitor centre. I just had to get a closer look.
The plants turned out to be Pyramidal Bugle Ajuga pyramidalis. My field guide helpfully describes them as 'bright purple', in bold, like that, so you understand how very purple they are. They are also hairy.
They like to grow in open grassland and on rocky ledges, anywhere from sea level to 2700 metres. Theoretically I could see them here in the Touraine, but I'm sure I would have remembered them if I had.