They work really well for stamping! I used 8 different Barry M Gelly colours for this skittle - a corresponding paler one for each of the 4 almost-black colours. I stamped using MoYou London Steampunk XL plate 7.
The red is the only one which doesn't work as well over the bright colour. The contrast isn't quite as strong as the other ones I chose.
These are Blood Orange, stamped with Black Cherry, Key Lime stamped with Black Pistachio, Fondant stamped with Black Currant and Guava stamped with Black Grape.
These work really well for stamping, and I can see them getting a lot of use from me this winter.