It is my understanding that buff stacking of the same type works off of slot number, so you can't stack more than one of slot 1 cold resistance, but you can stack slot 1 cold resistance with slot 2 cold resistance.
Based on that, the slot 2 cold resistance from
Aura of White Petals (the cold resistance buff from
White Flower of Functionality) should stack with the slot 1 cold resistance from the
Endure Cold/
Resist Cold/
Circle of Summer line. I don't have the flower to test on Blue, but on Green it does not currently stack with Endure Cold and Resist Cold, but it does stack with Circle of Summer. I believe it should also stack with Endure Cold and Resist Cold.