Also important to note, both H. appendiculatus and H. sp. rotkeil... and really all Heros species, I suppose... can vary widely in color, and they can also change color quickly. There are rotkeil that are more blue-green based, rotkeil that are more brown-yellow based, etc.
Heros are highly variable, even in fish from the same spawn or catch location. So it’s hard to go by color alone when identifying them. It’s easier to look at a combination of markings, number of bars, fin colors, etc.
Some people have really gorgeous blue-tinted rotkeils, and females will turn blue in the face when in spawning mode in most Heros species, but I’ve never been lucky enough to find a strain of blueish rotkeil. Mine are always more brown-based.