Moody

In this world, everyone can tell your mood by the colour of your hair.

Opal is an ordinary girl here. She has hair, along with everyone else. Her hair changes colour, just like everyone else's

Red means angry or jealous, or sometimes hate.
Yellow means happy or excited.
Blue means sad or disappointed.
Pink means nervous, anxious, or embarrassed (but you can usually tell by someone's cheeks when they're embarrassed).
Orange means love.

Purple, green, black, grey, white, and brown are still unknown.

Opal is just starting to wonder why she's really here, when she meets someone different.

And this different person might just cause the death of the world.