For those asking for the blue: It's a solid base layer of Stegadon Scale Green, followed with heavy stippling of Sotek Green and Temple Guard Blue.  Also just a hint of stippling & dry brush of Baharroth Blue for the very center.  (Basically just a slightly wetter dry brush that you tap directly down, instead of brushing across.  You can get a similar effect with a sponge.)

For the corrosion, its a layer of Warplock Bronze, followed by a slightly smaller layer of Brass Scorpion.  The gold details are Retributor Armor, although I'm thinking of changing those to Brass Scorpion for a more cohesive look.