I don't think it would be particularly difficult to do the actual colours, though matching the subtle but effective weathering job is another matter.
You'd want to base the entire tank in that drab colour - possibly Steel Legion Drab to be precise. I'd then Agrax Earthshade every single individual bolt, rivet and crevice - time-consuming but really makes the difference and adds great depth. Don't just wash the entire thing with it or else you'll darken all the flat areas and will need to go back over them all with the SLD paint. Take your time and individually wash the details. Then a drybrush with a lighter colour - possibly Ushabti bone? That would probably be a good match for the main colours.
Aa for the rest, Gorthor Brown looks a good match for the small brown sections as its not too dark and not too light. Rhinox Hide is darker so would be a bit more contrasting if you used it.
The bluey-grey would be The Fang, Dawnstone or Russ Grey depending on how much/little of that slight blue tint you want. The red looks like a darker one - Khorne or Mephiston Red?
It would literally just be a case of hand painting those small camouflage areas yourself. I've done similar things on Kasrkin carapace armour. It isn't tricky, but what makes it a bit more difficult than you'd expect is keeping it consistent and not going overboard with it. If I was you, I'd settle on colours and then copy those patterns bit for bit, then you'll have a good idea of spacing to be able to finish off the other angles you can't see.
Really, this isn't too hard to replicate in a decent manner - just a bit time-consuming and possibly tedious, but if I were to try it that is the route I'd go down. After all of the above it would be a case of weathering it as you see fit to make it look a little closer to that photo (the fading on the red panel, the dirt etc).
Good luck!
|