Skitarii Vanguard (can be applied to Rangers as well :) ) paint scheme loosely inspired by Purge Troopers from Star Wars: Jedi Fallen Order, as well as the Agripinaa scheme.

Prep note: If possible, do not attach your model to the base; it makes reaching the underside of the Skitarii duster much easier.

1. Prime with Black . If Vallejo Surface Primers aren't your bag, I'm certain that Chaos Black will do fine! Just make sure the whole model is a good, solid black.
2. Paint underside of duster with Mephiston Red . Thin coats until color is solid or otherwise to your liking. Also ensure edges of the duster, as well as the exposed end of the sleeves are painted Mephiston Red .
3. Paint all metal parts (hands, legs, backpack, armor, rifle accents, dangling cable bits) Leadbelcher . Even if the final result isn't that color, it is the foundation of all the other metals painted.
4. Paint the helmet, torso, shoulder, and leg armor Black Metallic . No need to airbrush, its coverage is great with a normal brush! Note: when painting the helmet, keep the "ears", ridges, and mouthpiece Leadbelcher for a nicer contrast.
5. Paint the rifle accents with Balthasar Gold . Which accents you paint is up to you, I just painted the scrolly sections and some parts of the barrel.
6. Paint the raised edges on the torso armor and the helmet ridge with Redrum . If you don't have access to it, I believe Vallejo also has a metallic red that should work. It may take a few thin coats to become a solid color.
7. Paint trousers London Grey . Clean up the legs as needed.
8. Paint the shell of the duster German Grey . Clean up edges of the duster and sleeves as needed.
9. Paint the leather straps on the backpack and the wood of the rifle with Rhinox Hide , being careful not to paint over the metal accents of the rifle.
10. Paint the helmet visor with Stormhost Silver , and then use Spiritstone Red to give the visor its red glow.
11. Paint the helmet lens above the visor, and the backpack lens over the shoulder, with Stormhost Silver . Apply a light dab of Temple Guard Blue , and put a dot of Ulthuan Grey in the middle of each lens to give it some life.
12. Clean up model, making sure that all tubes and cables are still Black ( Abaddon Black also works well)
13. Paint the white parts of the Cog Mechanicum with Ulthuan Grey (finicky business, I wouldn't blame you for skipping this part).
14. Wash with dark wash of your choice, taking care to avoid the blue lenses and the helmet visor. (I personally used Agrax Earthshade )

At this point, your Skitarii should look pretty complete. The following steps are just small cosmetic details, and I absolutely encourage you to go your own way with them if you have a different idea!

1. Mix 1 : 1 : 1 part Evil Sunz Scarlet Ulthuan Grey Ceramite White to create a slightly orangish-pink. Almost sort of like a Tums-color. Use that for the purity seals. Or you can just get a pink paint, that's probably easier. Use Rakarth Flesh for the purity seal paper. Wash purity seals with wash of choice. (Again, I used Agrax Earthshade .
2. Paint the small lightbulb on the backpack with Stormhost Silver , then Waystone Green for a glowing green light. Paint the hand on the backpack meter with Mephiston Red , and the buttons with Averland Sunset .
3. Attach model to base and base with Agrellan Badland , and paint rim with Neutral Grey .