While I couldn't quite match the look of the examples, I was still able to get a passable "mutant cactus" appearance with a white primer base, Delta Ceramcoat "Gecko Green" and a wash of Top Notch forest green for the base of the cactus, and then some light dry-brushing of the "beaky" tips with gold, pink, and then a bit more Gecko Green to blend the transition to the rest of the plant. This makes a great "mutant cactus" for alien plants or a pulp post-apoc wasteland.