dahlia1972 This was a pretty unique look as far as the dahlias I’ve encountered.
I had a Speckled Chee that sported mostly solid, and it was also a really rich dark velvety color with some stripes here and there, but not so purple, more red toned.
Debora Renae did the stripeys but in dark velvet red & crimson red.
Ryan C was my other that had such a dark velvety purple, but that’s a bicolor with white tips, and it didn’t get the stripes.
Sandia Bertha, Jennifer’s Wedding, Allen’s High Voltage, Berner Oberland, Le Baron, Purple Carnival, Diva, and Glenplace were the other purples I grew. Jennifer’s Wedding did get a nice range of deeper velvety purple on the center of the petals, and brighter purple on the edges of the petals.
Here’s Jennifer’s Wedding:
Sandia Bertha (I highly recommend this one if you like the looks; easy grower & good tubers):
I got open centered blooms from my Allen’s High Voltage, so will be trying new stock this year:
Purple Carnival had white stripes with varying shades of purple. Must warn you that they were small blooms & for some reason my plant had the floppiest stems ever. 
Le Baron did give a two-tone purple effect, but not the super deep dark purple like the HH Black Widow. It was very useful in bouquets. 
And since I got started listing my purples, here’s Berner Oberland which is only barely tangentially related to the conversation on hand, but I loved it, so any chance to show it off: 
