Prospero starts a deep clear red, then turns garnet (similar to Tradescant), and finally an actual mauve. Often you see all three colors on one flower as the petals age sequentially. It is a marvellous effect. Tradescant is a dusky burgundy red.

I love Prospero, but it is not always cane-hardy even here. This winter's low was around 5 degrees, and I had to cut two of my three plants nearly to the ground. Mike Rivers grows it as a die-back shrub in zone 5 Michigan. Its habit is short and twiggy, whereas Tradescant is rangy and ropy. Prospero has decent blackspot resistance for me.

Have you considered The Prince? It ages to a beautiful royal purple and stays small. It is best planted in multiples for the best effect.

Ruth

Of Tradescant, Prospero, and The Prince, The Prince is the most purple and has the best fragrance. Not particularly vigorous, but gorgeous. I think all three of those would require major TLC in zone 5.

What about a Portland rose, such as 'Indigo'?

Here is a link that might be useful: trospero's comments on 'Indigo'

As long as powdery mildew isn't a huge problem for you, Indigo may be your best bet.

We finally left The Prince in a location where he is surrounded by 'Flower Girl.'
In that situation, his occasional long-stemmed, rich purple blooms are a lovely occasional surprise.
Prolific 'Flower Girl' hides his weedy, upright "body."
Tradescant was a very sparse bloomer here.
But the plant we had suckered un-controllably -- so maybe a good plant would be a better bet.
'Prospero' is a terrific rose, best handled as one would a China.
Which is to say that Michael's comment that it is not cane-hardy isn't surprising.

Jeri

The Prince is a great purple rose. It is short and squat here and dies back to the ground during the winter but grows well in the spring.

I love The Prince, it's an outstanding rose. Wonderful bloom color and fragrance.

I lost my Tradescant after transplanting it, and am replacing it as the blooms were memorable, as was the fragrance. In my garden setting the blooms age to a fuschia/purple shade. It has a strong sweet scent.

William Shakespeare 2000 is another exceptional rose. The blooms have a scent like roses and violets. Blooms are not quite as dark as Tradescant, but still have a rich color with fuschia/purple shadings.

If you'd like to see pics, feel free to email me.

I have Tradescant and The Prince. I would show you pictures, but my camera shows them both as red. But Prince is purple. Tradescant is the truest red I have, the blooms turn purplish as they age and in the fall, but nothing compared to the Prince.

I would second the suggestion for Indigo for purple. Or have you considered Reine des Violettes for a very violet/purple color, gets taller than Indigo but won't sucker?

I just planted a couple "Rhapsody in Blue" shrubs last summer. (I planted one, then it was such a gorgeous color I had to get another.) If you want purple, this might be a good choice. They are some of the more purple/blue roses I have--not red at all. They seem like little bloom machines with a nice fragrance. No disease problems yet in my no-spray garden. I'm not sure what the final size will be--they seem to be staying fairly small and vertical so far. I've read that they are in the 4' range, but HMF says 6-7'.

Thank you, thank you all. Well Tradescant and Prospero are out, way out, Michael,rangy and not cane hardy clinched it. I knew if I shared my search with you all I'd get "THE" best possible choices. They are all beautiful. Powdery mildew was a nightmare last season so The Prince would not be happy here, thanks for the heads up Jerijen . The space could not take one that suckers so Indigo would not work. Reine des Violettes is not violet enough. Rhapsody in Blue is gorgeous, really purple, smallish and possible no spray. YEAH! I have been looking for so long. I found that Regan Nursery has it. Lucretial, is that where you got yours? I will have to baby her in my zone but I am more then glad to.Thanks again everyone. Elizabeth

If you live in upstate NY, I doubt that The Prince would get powder mildew.

Indigo is a beautiful rose. Would you consider Midnight Blue or Ebb Tide? I have Ebb Tide and absolutely love the color and fragrance. My neighbor has Midnight Blue and I really like that one as well. I love love love the wine red purple roses!!

I have many Austins, and I love them all...but I've been on a "real" purple quest too lately. In the end, I went with, Ebb Tide. Haven't gotten it in yet, but I'm hoping it lives up to everything I've read about it. It looks goregeous in pictures, and they say it smells even better. Got the fingers crossed here....and the eyes, the legs...etc.

Elizabeth, I just got my Rhapsody in Blue at the local nursery (year end clearance, too--woo hoo!). I think the color is FABULOUS! I also have Ebb Tide and Midnight Blue, but I just put them in as bands last fall so I don't know what they'll look like yet.

Can't have too much purple!

Lucretia, I added Rhapsody in Blue to my Heirloom order. Thanks for the introduction. Unfortunately I only have room for one. Midnight Blue was calling to me too, but no room. My Niece and DH are now in a new house. It is a new build which means a blank slate. I am their garden consultant. My Niece's favorite color is purple. Sooo I may be suggesting some roses I learned of on this thread. I have already ordered some purple and lavender Daylilies for her. So much fun. Elizabeth

I regard 'Midnight Blue' as far superior in growth habit, repeat bloom, color and overall garden-worthiness to any of the Austin red/purples, with the exception of perhaps 'William Shakespeare 2000'. All of the others, including the twiggy and shapeless 'The Prince' (it brings new meaning to the word "runty") have had very poor disease resistance and are very slow to repeat. Yes, I'm sure they perform well somewhere, but not in my garden. Tom Carruth's roses are far better plants for me.

Paul