A shard is a three color combination going around the Magic wheel of five colors, with the first color being the main color:
--Bant is White Green Blue.
--Esper is Blue White Black
--Grixis is Black Blue Red
--Jund is Red Black Green
--Naya is Green Red White
So there....when I read Naya I will think of a Green Red White deck!
Here is a link to my post on the ten guilds of Ravnica
Decks built around Nicol Bolas are Grixis decks if they stick to three colors.
Here are the obelisks and panorama lands from Shards of Alara.