Answer: Since it is October, this is probably a result of the weather with the plant beginning to change color prior to losing its leaves for the winter. You will need to protect the plant in some way this winter if you want it to survive, assuming it is a hardy variety. The roots will need to be insulated from the cold (you culd sink the pot in the ground or possibly heap a generous amount of mulch over it) and the plant should be kept in a sheltered location out of the wind. Many hydrangeas bloom on the previous year's growth, so it is important to minimize winter damage as well as to avoid pruning it before the next bloom season.
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