Unity is right about the pigment breakdown pattern, assuming a florescent or broad-spectrum light source, higher energy colors (purple, blue, green, etc...) will always go first.

And we have indeed had an entire thread about this before, someone previously noticed something quite similar between two of them. I believe it was either this year or maybe late to mid 2013. If I remember correctly, the theory is that the the ones which appear to be more centered are possibly later runs, whereas those that are less centered are from earlier runs, but no one is really sure. There is a severe paucity of information about them.