All olives begin life green. After that, it gets complicated. With so many varieties available, here's a breakdown of the most common to help you avoid the pits... 

Greek

• Black

Kalamata: large, mild, soft, vinegary

Royal: medium, meaty, vinegary

• Green

Naphplion: large, mild, meaty

Marinated: medium, with herbs and spices

Kalamata, also sold as Giant: large, meaty, can be bitter

Turkish

• Black

Uncured: medium, soft, wrinkled, milky flavor

Oil cured: medium, salty, milky flavor

Moroccan

• Black

Oil cured: medium, wrinkled, salty, smoky flavor

Lebanese                 

• Black

Small, grainy, slightly bitter    

• Green

Italian

• Black

Bella Cerignola: large, round, soft, sweet, bland, no pronounced flavor

Dry roasted: medium, wrinkled, slightly bitter

Gaeta: medium, soft, fruity

Dry Roasted: medium, wrinkled, slightly bitter               

• Green

Sicilian Green: large, juicy, salty, tart

 Spanish

• Green                                                                                     

Arbequino: tiny, round, greeny brown

French

• Black

Niçoise: small, milky, fruity, herby

Nyons: small, oil-cured, herby, full of flavor          

• Green

Provençal Green: soft, mild and herby

Picholine: light brown, soft, strong flavor

To store

If your olives are in brine, you can store them for a limited period in water that you refresh regularly. If they are olive cured, kept in a lidded jar covered in oil they will last pretty much indefinitely.

To marinate or cure your own olives

It's so easy to marinate olives there's no need to buy them ready done. Here's an excellent marinade and recipe from Culinate, along with the method for curing your own.