Salomé is a confused girl, to put it mildly. Standing toe to toe with Jokanaan, she can't seem to decide whether she loves him or hates him. Even when she declares that she will kiss his mouth, her motives aren't exactly clear; her lust is mixed with something more violent and forceful. This combination of the really dark and the really sensual defines Salomé.
The puppy love of the young Syrian, poetic and innocent, ends in suicide; and his death (and the blood he leaves behind) functions as a bad omen. There are moments of wit, but even they are tainted. Consider this exchange between the Cappadocian and the First Soldier:
THE CAPPADOCIAN: Yet it is a terrible thing to strangle a king.
FIRST SOLDIER: Why? Kings have but one neck, like other folk. (57-62)
The soldier's observation is as clever as it is ominous, and it's the closest thing Salomé has to humor. By the time Salomé has decided to dance for Herod, even that little bit of levity has totally vanished and is replaced with the play's trademark sexiness (the dance is pretty burlesque-y) and pitch-darkness (the dance ends in a girl making out with a severed head, guys.)