The only two hours that matter
The first hour after sunrise and the last hour before sunset are when the sand goes orange and every ridge throws a long shadow. Between about 11:00 and 16:00 the light comes from overhead, the dunes flatten out and even a good camera returns a beige nothing.
Sunrise is better than sunset for clean sand: the wind overnight erases the previous day's tracks and you will often be the first person on the ridge.