It may mean that the person is angry or irritated...talking about their emotions at the time. It will usually NOT mean that someone has put salt on them and tasted them! Hahahahaha! Good question and keep on learning! :)

A mix of bitter and jealous

"Salty" literally means "with the flavour of salt". I'm not sure if this fits your context, but "salty guy" may mean the guy is crying (ie. salty tears) because he thinks something is unfair.

'Salty,' describing a person, has several different meanings depending on the context.