I am looking for papers on bluing of red roses. I found one on this affect on red “ground”roses but lost the reference (help).
I have notes on a number of papers that may be relevant.
Some substances in a rose become more concentrated as the flower ages. Others fade. A red rose can “blue” with age as the quantity of co-pigment increases.
These folks attribute age related bluing in roses to be due to the cellular pH increasing with time and to quercitin complex formation over time.