Hello Richard,
hmmm.....colours - I'm a little 'anal' in this respect
I did some digging around and came up with different folks suggestions -
White RAL 9010, any white would do Humbrol 34 or 134
(Blue) Grey colour Ral 7031, Humbrol 27 or 125 (Too dark to me).
Brown RAL 8025, so Humbrol 186 or Gloss 10 + a touch of Satin brown 133
Or....
For the Grey - Humbrol Grey 28, VMC 883 or 152, or Tamiya XF55/XF54
Brown - Humbrol 29 or VMC 921 or 141
For the white - Humbrol 134 or VMA 71087 or 71005, Revel 69
Looking at my notes, I eventually went for..
The models were spray painted a white undercoat (Gamesworkshop skull white or whatever they call it!)
The grey is a thinned Tamiya XF66 light Grey
The Brown is Humbrol 186.
The models then received a localised 'pin' wash of Mig Productions Dark wash, I then lighly dry-brushed up some edges in the original colour.
To me it looks right in 1/300, it may not in a larger scale
Hope this helps?
Andy