Best thing I've heard about colder temps.
I had a Bl. Morning Glory or Maidosa bloom last year with almost no color; ir was so pale it was just off-white, previously it had a lovely violet cast.
How about light affecting color? My Mtssa. Royal Robe 'Jerry's Pick' finished blooming with the deep, rich burgandy color and all the same color. I got a new bench and light for the greenhouse and stuck ithe plant right under the light. Well I sunburned many leaves
and the flowers that just opened are paler in color and show more variation.