To create the effect, first stamp an image in Versamark on black card, then emboss it with black embossing powder. Next carefully paint inside the embossed lines using bleach until the black is faded - make sure you use a cheap paintbrush as they get ruined by the bleach (I got through 2 of them!) Depending on the card it may take several coats of bleach but let the card dry between coats, or use a heat gun to speed up the process, so you don't overdo it. This was Papermania Capsule Collection card, and it took 4 coats.
Once it was fully dry I used watercolour pencils to colour in the image. Other coloured pencils such as Coloursoft or Polychromos would probably work, too. My first attempt was done on the textured side of the card but the texture still showed & it didn't look right for this particular image so I tried again on the reverse - smooth - side of the card and it gave a much better finish.
I kept the finished card simple which is how I think it should be for a such an occasion.
Lily stamp - Craft UK, white card blank Craftwork Card basics, black card Papermania Capsule Collection.
* I've since seen the black magic technique described as stamping the image with white ink on black card & colouring over the top with different media (pencils, Copics etc). I have no idea which is the correct definition of the technique!