The look of planet is basically inspired by Pandora in Avatar!
  Very plantation like and exotic color, purple!
  I'm trying to come up with idea what kind of components create this planet's atmosphere.

Vioturn

Introducing the world I created and I call "Vioturn". This world, unlike earth whole plantation has violet coloration to it. Also water is very saturated and different color. This world is completely designed for nature to grow to unlimited size. Therefore its components of atmosphere is completely different from an earth.