Actually, most of the day they look yellow.
They'red only if you wake up at 04.30 in the morning and get there around sunrise to be able to appreciate the color.
It's a pity that half of the area is marred by Vietnamese kids offering "slide down" from the dunes experience to all tourists, effectively destroying the environment.
Don't be fooled by the simplicity of the picture though. Take a second look at the pastel colors, relaxing shapes and reflection of the dunes in the sky. It's one of the better photographs that we did during the trip so far.