“This particular dune, appearing like turquoise blue in enhanced color, is made of finer material and/or has a different composition than the surrounding.”
That was stated by NASA.
It’s a colorized photo. It’s an edited photo.
It could be a photo of a sand dune on Earth if we are to question authority but in this case the authority has made it perfectly clear that the photo is enhanced with this blue color.
There is no such things as blue dunes anywhere except on planets that unicorns live on and there are many of those where humans live.
That fact of course will not be Earthlings top priority as the entertaining fantasticals rule.
Feature image by NASA in the public domain