Synonyms that simplify each word to make it easier to understand:
melancholic - basically feeling sad or depressed
sanguine - There are different definitions of this word but I'm going to assume that you are talking about this one: optimistic/positive
choleric - grumpy
phlegmatic- self-confident
An overt flirt is phlegmatic
You have to be confident to be able to flirt properly or else it doesn't work very effectively
Hope this helped!