Color is not really a good way to ID Goby, because they can change on moments notice.
Take the Eleotris below, all pics are of the same fish, in different moods, in different habitat (certain plants) or when hunting (even when facing up, or facing toward the substrate).
You may want to compare the anterior dorsal, in marmorata it stretches almost into the caudal, in melanoma it is shorter, and both are native to Viet Nam.