I've ordered some extra paints and think I have narrowed down the colour scheme.
Basecoat of vallejo dark german yellow primer (no. 2)
Followed by zenithal highlight with vallejo german dark yellow (no. 3)
Airbrush a shade with vallejo yellow green (no. 5)
Then paint on the edge highlight vallejo german yellow (no. 4)
And then paint on the shade in vallejo US olive drab (no.1)
I'll then do some more selective shading/glazes with nuln oil and brown ink, and highlight again if necessary
Hopefully that will give a more balanced colour scheme than the one currently.
Number 6 is vallejo camogreen used in the previous colour scheme and mixed with brown so I think the new colours are a good solution, as their all a bit browner.
Let me know what you think!