[Idontevensmoke]

1.) From a grower, dropping your temps does affect potency, by all means. Parts of the plant (such as you mentioned) turn people due to cold weathering and stress, but does not exclude genetics.
2.) Putting your bud in the freezer does not turn it Purple. I keep my weed in my freezer, I do not have purple weed, in fact, it is the best way to preserve my bud.

And finally,

3.) Strains such as PPP, GDP, Purple x kush's and haze's are genetically predisposed to producing "purple" buds. Some other strains that have purple characteristics are also genetically predisposed to attaining purple shaded fan leaves.