Actually, color has nothing to do with it, since seahorses can all change color; and true kelloggi get much larger than the typically accepted kuda, and usually larger than reidi as well.
It is the shape of the coronet, and the fact that it has a rounded backward pointing tip. H. kelloggi have more tail rings, a higher coronet, and more prominent cheek and eye spines. Also, H. kelloggi have a tendency to have thin vertical lines running up and down their body made up of tiny spots; rather than the randomly placed large spots usually found on kuda.
That all being said, your seahorse does have a rather high coronet for kuda, and it is possible that it is a kuda/kelloggi hybrid; but IMO not a true kelloggi.