I had a bit of time so took a break from work and spent half an hour in the garden; they were basecoated with Wilco black satin hobby paint (surprisingly good and 1/3rd the price of GW spray cans).


 

Then Army Painter armour grey


 

Then Tamiya Panzer grey


 

Then Tamiya gunship grey


 

Lastly Tamiya ocean grey


 

So they fit the theme fairly well now. 


 

They need the obligatory glowing orange eyes


 

And (hopefully subtle) washes of various colours for tone, contrast and visual interest. 


 

Finally some actual detailing for particular items like smoke grenades and flamer nozzles.