Aura of White Petals & Resist Cold do not stack, but they should
 

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.

The circle line has one that also stacks with the same line of resist. I forget which one but it is very useful. They also block Occlusion of Sound from a Bard (PvP server) which must correlate to the slot thing you are mentioning.

So I do think you are correct Kirdan. Nice find. Thanks Nilbog for taking the time to look into all of this stuff.

So, buff stacking hasn't changed much on live since the classic era, which means that for the most part we can rely on live spell stacking data to determine stacking here (there's always the possibility that stacking changed, and if so you'd need to talk to a classic researcher).

https://lucy.allakhazam.com/ is the king when it comes to that kind of data, and we can see that on live EQ ...

The Aura of White Petals (https://lucy.allakhazam.com/stacking...76&source=Live) and Circle of Summer (https://lucy.allakhazam.com/stacking...52&source=Live) should stack: neither is listed on each other's "Stacking" list, and those lists indicate the Aura is slot 2 while the Circle is slot 4.

This is all (correctly) reflected on our wiki's buff lines page (which I made largely based on the Lucy data): https://wiki.project1999.com/Buff_Lines#Cold_Resistance

P.S. I tested on Blue and confirmed that the flower overwrote my Resist Cold.