This was how I painted my first seven Plague Marines, for later models I shifted towards a more brown than green

1. Primer Russian Green 4bo and Stynylrez white primer zenithal highlight

Green Armour

1. Base Coat 2:1 Russian Uniform WWII and Uniform Green
2. Wash Athonian Camoshade
3. Edge Highlighting Light Green

Copper Trim

1. Undercoat Gun Metal
2. Layer True Copper
3. Wash Nuln Oil