Princeton, are you in Princeton, NJ? If so, your soil will be acid to at least some degree. It is important in influencing color on big leaf hydrangeas.

I believe it is - my colored hydrangea (most of mine are white) blooms pink.

p.s. yes, I am 2 miles from Princeton University.

If they are blooming pink, then your soil is insufficiently acidic. And purple is not really a standard hydrangea color - it is typically the result of a very intensely blue colored hydrangea (Enziandom, Hamburg, etc.) in less than ideally acidic soil or a deep pink flowered one growing in a more acidic soil.

Get your soil pH tested and let us know the results.

Let's Dance Rhythmic Blue from Proven Winners is relatively new, a cousin of Endless Summer original, and fairly easy to get purples out of because it tends toward deeper colors throughout the pink-blue spectrum.

Springwood, thanks for the suggestion! I actually found it at a local nursery (see pic below). The different colors of the blooms makes it so interesting, as well as the lovely purple of the final bloom.

Congrats on the buy! With proper care it should come back similar to that year after year, regardless of freeze damage.

They really do continue keep leaning toward the deeps and darks, especially toward the end of the bloom's life. From what I've seen, sister plant Let's Dance Rave performs similarly, albeit slightly more bright and less dark. The more compact, shyer blooming Cityline Venice and Paris are capable plants as well. Paris is more red-oriented but turns purple quite easily.