Ok, I've had a check and the colours I have used in the past are as follows:
Base coat silver - Humbrol 191 Chrome Silver (do not touch for at least a day and wear latex gloves to avoid fingerprints)
Dome and cheeks - I can't seem to find the HUmbrol paint I used on one of my helmets, it was a couple of years ago now. Try looking at the following link http://airfix.com/cs/resources/paints.aspx
I thought that some of the colours on there may do.
For the upper cheeks I used Tamiya XF-11 JN Green or XF-27 Black Green
For mandibles I used some automotive paint I bought from Halfords. The only thing with automotive paints is that they are not acrylic and take longer to dry, and because they are designed for cars, they dry to to be tough, making weathering a bit harder. I would recommend spraying them from futher away than you would with acrylics.
Try this link for a list of Tamiya paints
I would seriously recommend trying airbrushing though. On my latest helmet I mixed my colours and I personally think it is the best option.
I hope this helps