Hi Bobble! generally both paints are mixtures of colours; Shadow Colour is usually a fairly weak mixture of Blue and Red - something like Ultramarine Blue and Alizarin Crimson and sometimes with other slightly darker colours, the idea being to paint it over areas where you would expect shadows to be, whilst still showing the details underneath.
I don't know Country Olive, but I guess its a mixture of Blue and a Warm Yellow, to give it that kind of Olive green.
You'll probably find that different manufacturers will use different mixtures for these two colours, but I hope the above explanation will give you an idea what to expect.
Very best wishes,
PA & RSC Wigan / Warrington / St Helens