Hello, and thank you for contacting us about your hydrangeas. It appears that the shrub closer to the building does not have the purpling leaves. This leads me to suspect that the purpling is due to the weather, specifically warm days and cold nights such as those we have had in the last few weeks. This should not harm your plants.
If you have not already done so, I would suggest adding about an inch of mature compost or manure over the drip line of each plant. You can also prune out any dead stems.
If you notice any other symptoms or the green plants begin purpling, please write again. However, I think your shrubs should be fine.
Thx so much for the response!