Thanks
@Calif_Sue I hadn't thought about the night-time temps! I think you mean the night before it opens having an impact on how recurve and aspects of coloration may appear? It was indeed a return to colder nights before (and after, for that matter) when this one opened, following a string of very hot days earlier in the month. Weather history shows that the temps had dropped about 15 degrees after the warm spell, and before this one bloomed.
So, yes, definitely a cooler morning when it bloomed.