caroline — yes, caroline's will is incredibly strong and she's notably strong and in control of herself as a vampire, but she's a teenage girl with low self-worth so :)
grace — yes!
pearl — yes!

caroline — caroline's aura is like a solar eclipse, she's a bright golden yellow, warm and clear, inviting, inevitable, except the darkness of vampirism is constantly trying to eat away at the sunshine
grace — grace's aura is half a rainbow, pale green shimmering into a lot of yellow before a ring of orange and red, it looks energetic and hopeful, cheerful and very alive, but the edges of the red and green feel scared and ruined, like creeping rust or acid, her bright yellow and orange is very strong though
pearl — pearl's aura is pearly white, almost iridescent, reflecting off the colors around her, almost a mirror since her ability is being able to manipulate the threads of other people's magic, so koby would probably see a paler reflection of his own aura one on one and bits of other people if he's looking at her talking to other people