I thought I'd have a try at painting a batch of the good guys (basically, humans in space armour) with GW's contrast paints. The main reason for this is that the models can be largely one colour and have plenty of bumps and creases in their outfits where the contrast paint could "catch". I used Black Templar, which is the standard black colour, over a simple white undercoat. I painted ten models.
The contrast paint works rather well on the bumpy armour, although the end result isn't black really as much as a dark green-grey. It reminds me of the Alien's skin. I added some colour with the visors (which have come out a bit too luridly blue for my tastes), red shoulder pads and a stripe of orange on each gun, presumably to indicate glowing power levels of some kind. The orange was also done with contrast paint over white, and I think it works well.
The contrast paint isn't perfect by a long way, and does create slightly odd shading in some places. But it looks decent, especially given the length of time it took to do. I think these guys will work well as henchmen and enforcers for some kind of cyberpunk corporation.