Festival Xayah / Rakan??
So, I was thinking about my new secondary character
, and about
. Then, this amazing idea popped into my head. I remembered Festival Queen
, and that
and
love dancing. The dark color scheme of the Festival shows
while the bright, lively colors show 
Ideas:
Recall: They do the tango together.
Powers:
:
Q: She throws two fireworks leaving behind a colorful trail.
W: She throws firecrackers
E: The Fireworks come blazing back to her. The root would be a sparking, colorful thing. It would also explode creating a firework explosion above her rooted enemy.
R: She throws several fireworks.

Q: He throws out a party streamer. The heal would be multi-colored and upon healing it would play a short clip of music.
W: Same, but different colors (maybe a conga-drum bash sound effect?)
E: More colorful shields
R: Enemies charmed instead dance their way forward, while fire crackers sound around Rakan.
Theme:
It does fit. They could be celebrating a victory for the Vastaya through music and dance.