While jealousy and envy are very real emotions, it is almost impossible to predict how this will be displayed. Some people feel intense jealousy but have learned not to show it, because we are ashamed of these feelings. Someone who is jealous (e.g., someone who thinks his lover has a sexual interest in someone else, or someone who is worried about losing a friend to another) or envious (e.g., someone who desires what someone else has) may appear angry at about the perceived betrayal or about the unfairness of the situation, while another jealous or envious person might seem more worried or sad.
Thus, jealousy and envy might be thought of as causes for other emotional displays rather than emotions that you can “read” directly. Generally, we infer that someone is jealous or envious (unless they confess this directly).