Aura

Estrella has the ability to feel other people's emotions and see them as auras.

Colors
Black - hate


 * Heron had a black aura after being near a demon.
 * Isaac had a black aura when around Estrella (chapter 39).

Pink - embarrassment


 * Bella

Yellow - A yellow aura is warm.


 * Heron (chapter 11)

Gold -


 * Estrella says that Elias had a gold aura in chapter 11.

Red/Burgandy/Black aka "Fireworks" -


 * Elias, Karijan, and Marquess Kelpy.

Purple


 * Baron Silidin (chapter 27)

Blue - sadness, pain, misery, and heartbreak


 * Isaac had a blue aura (chapter 39).