Ethics consists in the study of the good and the evil. Basically good and evil are discernments, mentalities, one mentality is benevolent, edifyng, progressive this mentality is call "good mentality." There is another that is destructive, chaotic, unfair, we call this "bad mentality".
We live according to the spirit, that is, we live righteously; or we live according to the flesh, that is, we sin, as the Gospels teach us. The Parabola of the Good Samaritan tells us that in front of the neighbor we are righteous or sinful, we choose. In this sense there are no "grays", things are either "white" or "black".
We hit or we fail, we are false or truthful. In this consist the study of ethics.