Based on TireKhorne's work on the 40k Homebrew site.

The main colours are red, blue, and gold.

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 Games Workshop spray cans and brush on paints.

Priming:

I find the metallic sprays from GW tend to be a little on the transparent side, so an initial undercoat of grey helps.

1. Prime with Mechanicus Standard Grey
2. Prime over that with Retributor Armour

Gold (Armour Trim)

I generally start with the armour trim so that any time I get paint on another piece its easy to cover later.

1. Drybrush over with Retributor Armour to even out the colour
2. Shade the recesses with Agrax Earthshade
3. Highlight the fine points and sharp edges with Stormhost Silver

Red (Armour Panels)

1. Base with Mephiston Red
2. Shade the recesses with Agrax Earthshade
3. Highlight the edges with Evil Sunz Scarlet
4. Finer highlight with Wild Rider Red
5. Highlight fine points with Fire Dragon Bright

Blue (Shoulder Pads and Details)

1. Base with Sotek Green
2. Shade the recesses with Drakenhof Nightshade
3. Highlight the edges with Temple Guard Blue
4. Finer highight with Baharroth Blue
5. Highlight fine points with Baharroth Blue mixed 1:1 with White Scar

White (Cloth)

1. Base with Celestra Grey
2. Shade the recesses with Agrax Earthshade
3. Layer over most of the cloth with Ulthuan Grey leaving the recesses dark.
4. Highlight the edges with White Scar

Black (Armour Ribbing)

1. Base with Abaddon Black
2. Highlight the edges with Eshin Grey
3. Highlight fine points with Dawnstone

Grey (Details)

1. Base with Mechanicus Standard Grey
2. Shade the recesses with Nuln Oil
3. Highlight the edges with Dawnstone

Silver (Details)

For grenades, replace Nuln Oil with Athonian Camoshade

1. Base with Leadbelcher
2. Shade the recesses with Nuln Oil
3. Highlight the edges with Stormhost Silver

Brown (Leather)

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