Right now, so many of the garden blooms are purple.

 
Allium:

Bee balm:

Blazingstar:

Phlox:

(I’m choosing not to include the invasive creeping bellflower, though it is purple.)

But is this joe-pye weed pink or purple?

 
Color is indeed subjective. I would say these flowers are pink, but they’re called purple coneflowers:

I would definitely call this one purple, but its name is blue vervain:

And this is purple giant hyssop, but it looks less and less purple every year: