This is my take on the paint scheme of the Ordo Sinister featured on the Forgeworld Warlord-Sinister Knight.

The main colours are grey and bronze, with red and green elements.

General Information:

My general method is to lay down all the base colours for the model, then do all the shading in the recesses before moving on to the highlights.

I don't own an airbrush, so the recipe will mainly consist of brush on paints.

Priming:

1. Prime the model with Mechanicus Standard Grey

Dark Grey (Armour Panels):

1. Drybrush over the model with Eshin Grey to even colour
2. Shade the recesses with Nuln Oil
3. Highlight the edges with Dawnstone
4. Highlight fine points and sharp edges with Administratum Grey

Bronze (Armour Trim):

1. Base with Balthasar Gold
2. Shade the recesses and around any rivets with Agrax Earthshade
3. Apply thinned Incubi Darkness as a verdigris effect
4. Add a thin layer of Kabalite Green to increase the definition of the verdigris
5. Highlight fine points and sharp edges with Stormhost Silver

Red (Details - Lenses, Cloth, Wraps, Weapon Casing):

1. Base with Mephiston Red
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Wild Rider Red
4. Add fine points with Fire Dragon Bright

Silver (Details - Weapons, Chains):

1. Base with Leadbelcher
2. Shade the recesses with Nuln Oil
3. Apply thinned Skrag Brown as a rust effect
4. Highlight fine points and sharp edges with Stormhost Silver

Black (Details - Armour Ribbing):

1. Base with Abaddon Black
2. Highlight the edges with Eshin Grey

Brown (Details - Leather Pouches):

1. Base with Rhinox Hide
2. Shade the recesses with Agrax Earthshade
3. Roughly highlight the edges with Skrag Brown
4. Add a fine highlight of Ushabti Bone

Tan (Details - Bones, Teeth):

1. Base with Rakarth Flesh
2. Layer the upper half with Skrag Brown
3. Shade over with Agrax Earthshade
4. Highlight raised portions with Rakarth Flesh