If you are asking about the bloom Endless Summer Blushing Bride's blooms turn red as the bloom ages. If you are referring to the foliage I have no idea. You can google the Endless Summer blooms to see the exact color.

My origenal endless summers blooms have a frosting of maroon now. They went green then a yellowy green then got a purple tinge to them now maroon.

You cannot with any degree of certainty determine a cultivar of H. macrophylla simply by color of the aging blossoms. There are far too many variables, including soil conditions (which can vary from area to area even within the same garden), climate/weather, sun/shade, watering habits, fertilizing methods, etc. -- all of these can have an impact on how both the blossoms color up initially and to what color they age.

The only truly reliable way to determine what cultivar this may be is to ask the neighbor. If they don't know, take a sample of a fresh blossom (not an aged one that has already changed color) to a good retail garden center and ask their opinion. Even if you were to get the exact same cultivar, that is no guarantee that the flowers will develop the same appearance as the neighbor's when they age.

FWIW, virtually all hydrangea blossoms will go through a series of coloring depending on the growing conditions and the age of the flower -- they are all appealing in their own right.

I have a few twist and shout hydrangea.

The blooms are pinkish with a blue hue. Apparently they'll be "more" blue in acidic soil.

They are supposed to get a showy maroon fall color. I did see it on plants in containers but that was late september.

Mine were still green on Friday night...we had a freaking freeze last night. The leaves are now BLACK and limp!

Not sure what your zone is, but Bluebird is supposed to have blue flowers and showy maroon fall color as well.

I have asked the neighbors which hydrangea they own and they didn't know. Perhaps when I get to know them better, they'll let me have a few stems so I could take cuttings. I did notice another hydrangea in our town which had flowers that turned maroon instead of brown so I have no idea whether this is the luck of the location or a certain variety. Both have been large mature mopheads. Will I end up with an entire yard filled with hydrangeas as I proceed with this quest? Probably, as it's certainly in my nature. Anyway thank you all for your comments. I now know a lot more about hydrangeas than I did a few days ago.