A picture of the blooms would help tremedously. A purple color simply indicates that the soil pH for this shrub is between neutral to slightly acidic. The green color at this time of the year is one of those color changes that H. Macrophylla blooms go through in the late summer months or in the Fall. So basically, we need more information because to start, hydrangea blooms by themselves can be quite difficult to identify. If you cannot post pictures, an option would be to look at a book with hydrangea bloom pictures in a library.

Some hydrangea varieties that you could check with a book: Geoffrey Chadbund, Hornli, Purple Tiers, Blue Wave, Blue Bird, Purple Passion, Miss Belgium.