The model has now had a coat of primer and here I used badger stynylrez neutral primer which is a kind of yellow. It's actually really close to the banana custard shade of yellow the British army used in Iraq at the time. It might be slightly darker but I will experiment and see if adding a touch of white primer to it and maybe a little bit of thinner will produce the shade I want.
Slightly lighter in tone would work better as with weathering the colour will darken somewhat. If that works it will save me having to mix up any more paint. As usual the primer has gone down flawlessly and has really popped the details on the model.