Here is my attempt at replicating classic Genestealer colours. These were typically used on old school Space Hulk Genestealers, as well as Genestealer Cults.

Dark Blue Carapace

1. Basecoat with Kantor Blue ,
2. Wash with Nuln Oil .
3. Reestablish the original blue with a drybrush of Kantor Blue .
4. Chunky edge highlight of Alaitoc Blue .
5. Fine edge highlight of Hoeth Blue .
6. Selectively highlight corners, points and prominent edges with Blue Horror .
7. Add specular highlights of Ulthuan Grey to points and within the previous stages highlights (where relevant).

Light Purple Flesh

1. Basecoat with a 1:1 mix of Daemonette Hide and Warpfiend Grey . This will likely take a few coats.
2. Wash with Druchii Violet .
3. Highlight raised areas with Warpfiend Grey .
4. Add finer highlights of Slaanesh Grey .
5. Mix the Slaanesh Grey 1:1 with Pallid Wych Flesh and selectively highlight more prominent areas.
6. Use pure Pallid Wych Flesh for specular highlights.

Black Claws and Spikes

1. Basecoat with Abaddon Black .
2. Edge highlight everything with a thick line of Dark Reaper .
3. Highlight everything again, this time with a thin line of Thunderhawk Blue .
4. With Fenrisian Grey , selectively highlight corners, points and prominent edges.
5. Finally, add small highlights to the centre of the previous highlights with Blue Horror . Try to make them very small, dots if at all possible.