red wines leaves purple stains

My mom has a hydrangea plant in her yard that slowly turns a deep wine red color over the duration of the summer. It’s almost as if the petals are getting a deeper and deeper tan all summer long. I clipped some branches to put in a vase in her house, and when they eventually dried out, they turned this beautiful deep lilac purple. As much as I like a nice oxblood red, I think I prefer the purple more.

dried hydrangea flowers