The photos of Elvis in his green jacket might have been printed in a larger quantity, or maybe they sold far better than the photos in which Elvis is wearing a pink jacket. Fact however is that the green jacket photos are very rare nowadays while the pink jacket photos are nearly impossible to find.
Notice also that girls in the background have been photoshopped out of this postcard.
Sources: http://www.elvisechoesofthepast.com/the-moss-photos-1956/