Elizabeth Carter leaned heavily against the wall, a red handprint on her face. Her eyes, huge and soulful, were sapphire blue, and at the moment, her lovely face was crumpled with pain. Annabelle, the girl who had done this, hissed furiously,"I'll do worse if you meddle with me, child."
Elizabeth glanced down at her amulet and saw it start to glow red. She glanced up, trying to keep her eyes hidden, but Annabelle had already seen the red, black and violet colours that where swirling in her eyes. Elizabeth stood, her instincts taking over her body. She snatched Annabelle and growled, "I'll show you what I can do, Anna."
Without another word, she leaned her head back, and then dove forth, teeth drawing the precious blood Elizabeth need to survive. Her eyes turned completely violet, as she drank. Annabelle screamed, nails scraping and cutting Elizabeth, but no blood came. Finally, Elizabeth released her, eyes glinting dangerously as she slashed her own wrist and poured it over her.
Elizabeth walked away, calming herself. Just before she faded away into the dark night, she called back casually, "Oh, and Anna, you're a vampire."
Annabelle Smith woke, drenched in sweat. Her chest heaved as she tried to erase the terrifying memories. You see, Anna was a vampire, and she had been so horribly cruel, all that time ago. Now, her eyes, which where green in the day, turned brown when she was bloodthirsty. Her turning had been a year ago, so she was relatively young, but her age still appeared to be twenty. Anna had changed, that much was for certain, and she would never be the same...
The eyes tell when they go vampire. the natural eye color mixes with red, and pain helps propel them into their , er, unusual hunger. Anger does the trick too. And, You have to bathe in the blood of the person who turned you, just in case this isn't clear.