I have noticed the same thing among red-purple bleeding hearts. They would live on that color and structure forever, until they eventually (after 3-5 days) dried up—living conditions? All but palatial; at the oddest of places, besides the floor mat in my car! Inside my garage where bad fumes rule, no sunlight, no fresh air, no water 2. Petunias would sog and sigh, but then that's how they are- thin, fragile, shriveling and crying at the hint of water or air. But even if the dermas shrink beyond recognition the colors would be intact without any external preserving treatment.
I am guessing it is the anti-aging activity of anthocyanidins in the petals? Delphinidin, Cyanidin, Petunidin and Peonidins 3 (?)
Another observation I can't ignore is the difference of colors in common (not the ones you buy from specialty markets) fruits and flowers in India and here (north east US). I am not saying that you don't get yellow flowers here, but the ratio of red-orange-yellow to blue-purple-red is much higher in India than here. Think mangoes, oranges, pineapples; compare that to grapes- concords, reds, cranberries, strawberries, raspberries, blue berries…. Think marigold, hibiscus, Krishnachura/ Gul-mohar (whatever the name is in English is eluding me now) and compare petunias, violets, pansies, daisies, delphinia. I grew up seeing yellow chrysanthemums at my mom's garden back there and now all I buy are purple ones. I believe the way we are going with genetics, "we are literally living life in Technicolor" even going all natural I don't say that you wouldn't see yellows and reds here and blues and purples there but its the ratio I cant ignore. Over here, a little south, and you have oranges in Sunshine state of Florida. And in India, you go a little north and beautiful orchids in every shade of purple welcome you, so do red apples. Is it the temperature then? Sub-tropic vs. temperate?
One huge (you might disagree on the huge) exception to this rule are lantanas. The prettiest are the pink-white-purple combinations so rampant in India but all I get here are red-yellow-oranges. Hmmm. Any ideas?
1 I am giving that (redderàbluer hue transition) to the increased alkalinity in water that I put the cut stems in (?) "anthocyanidins are highly conjugated chromophores. When the pH is changed, the extent of the conjugation (of the double bonds) is altered, which alters the wavelength of light energy absorbed by the molecule. (Natural anthocyanidins are most stable in a very low pH environment; at pH 8.0, most become colorless.) At pH 2.0, peonidin is cherry red; at 3.0 a strong yellowish pink; at 5.0 it is grape red-purple; and at 8.0 it becomes deep blue". Or would it be simple old-age?
2You can say that the phloems aren't carrying any water to the latter flowers. So water or no water probably doesn't count.
3 You've probably noted the similarity in names of some flowers and these chemicals. Like Peony and Peonidin, Petunia and Petunidin, Delphinium and Delphinidin. Cyan probably is from Blue. Antho meaning flower would give anthocyanins and anthocyanidins. [Anthocyanidins= Sugar (moiety) + anthocyanins.] So I am guessing cyanidins or anthocyanins were named from bluish pigments extracted from flowers and then as the others were discovered, they got named after the source. Later probably it was discovered that the same compounds exist in fruits and that is when it got popular among the non-scientific community. (Etymology)
