So all cannabis pretty much has the color already there to some extent. It is just cold, or other practices can get rid of the green chlorophyll to reveal the purple. The color in and of itself has nothing really to do with potency or smell, however possibly because the chlorophyll has been broken down, the smoke might be smoother, or less harsh.
Some strains have more of the anthocyanin, and so the purple can show even more, and this might indicate that it comes from a strain that is probably bred for strength/potency, maybe a strain of Hindu Kush or Columbian ancestry, and so maybe more potent than others, but it is by no means a guarantee as there are also very purple indica strains that are not very potent and are very purple. So the anthocyanin doesn’t really seem to be for anything other than color.
~MacG