Good "Sand" color

Personally I like MM Sand. It is a bit more saturated than many sands.  I also use it as a base to mix variations.  I mix some of the sand with a bit of white for natural (flax?) fabrics, as in non-cotton sails, and for linen covering on early or pre-WW1 aircraft.

Desert sands varies quite a bit in hue depending upon the geology of the general area. Shades can range from whitish or grayish to yellows, reds, or browns. Your best bet is to find some good reference photos online, then custom mix the shade you want going off of a base color in the general neighborhood. For example, start with something like Tamiya Deck Tan then add Dark Yellow or Desert Yellow to give it a more golden shade. Make sure that you mix up plenty, or keep a good record of how much of each color that you use because mixing up identical follow up batches is chancy at best.