Terra's hair falls to one eye when she's doing bad things - reflecting Slade's one-eyed look; When she regrets her actions, her hair falls back to show both eyes.
In the comics, Terra's betrayal affects the Titans for quite some time in the comic books. Changeling [Beast Boy] blames Deathstroke [Slade], and later realizes Terra was evil before Deathstroke met her. And for a while, the Titans have trouble trusting new people.
This episode is based on the comics when Terra betrayed the team in the classic "Judas Contract" story in "Tales of the Teen Titans" #42-44 and Annual #3 [1984]; She used the Titans secrets and weaknesses against them.
The comic book Terra is much more unstable and evil than her animated counterpart. She smokes and drinks and hates the Titans for no reason. When Slade and Terra's scheme falls apart, she loses any grip she had on sanity. She's so far gone that she uses her powers to create earthquakes that consume her in a mountain of debris. Beast Boy later finds her dead body. The Titans gives her a hero's funeral and don't reveal to the public she was a traitor. It all happens in TALES OF THE TEEN TITANS Annual #3. But the comic book Terra never shows an ounce of remorse.
The series' theme of reflections continues in the Terra arc; The mirror Beast Boy gave her in BETRAYAL breaks in the opening sequence.