Answer:
You could look at their body language, someone that has really good posture normally may slouch when something is wrong, Or in my experience their eyelids may even only be halfway open if the person is normally really cheery. But a huge one for me is how they talk, some people are able to keep a cheery tone of voice when something is wrong,but other people talk slower or can just sound kind of sad.
However if we are talking about the anger spectrum, there are multiple possibilities that really just depend on the person youre trying to read. As stated before, body language is a big one, some people dont really let anger effect them a lot. But, other people may just keep to themself, not look or talk at anyone or they just really look like they want to punch a wall. Also again, tone of voice. If their voice sounds harsh or they are getting loud those are pretty big signs.
hope this helps!