Rosa 'Veilchenblau', a near-blue rose.

A lot of the reference photos you'll see of this lovely violaceous single rose tend to be blown-out magenta in tone.
I suppose it's because so many photographers (myself included) love late-in-the-day angled light with its associated warm colour shift.
This is I think a much better representation of this rose (captured here under bright hazy light); it really is near-blue.
Nice scent too.