What is items' Rarity?

In Battle Campaign, there might be a task to upgrade equipment with a specific rarity. To understand what rarity each item has, you can check the item's color.

White - - Rarity 1

Green - - Rarity 2

 Blue -    - Rarity 3

Purple -  - Rarity 4

Yellow -  - Rarity 5

Orange -  - Rarity 6