For modern US desert sand I use Testors Model Master Sand, FS # 33531. It is a perfect match for current sand CARC paint. With a little weathering, it matches the vehicles I have served on in Iraq and stateside. Many use MM Army/Marine Gulf Sand, but it is too dark for me.
For 3-color NATO scheme, I use MM Flat Black, Medium Green, and Field Drab. These are lighter than the Tamiya NATO paints and than most recommended colors of Flat Black, Military Brown and Forest Green. It looks like the actual vehicles since they fade very quickly and never look as bright as the actual colors of Flat Black, Forest Green and Military Brown. Hope that answers your question.
Gino P. Quintiliani - Field Artillery - The KING of BATTLE!!!
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"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf." -- George Orwell