Energonicons, crystals, and accessories in the game are of different rarities. Each rarity has its color used all around the game. There are the following rarities available:

Common – White color
Uncommon – Blue color
Rare – Green color
Epic – Purple color
Legendary – Gold color

You can view the rarity of a crystal by tapping on it in your storage.

The rarity of an Accessory can be checked by looking at the color of the outline in the icon.

Energonicon’s rarity can be checked by looking at the outline color of its icon. You can also view your unlocked Energonicons and their rarity at the top of the page while in the Pig Lab.