The Seven Sages are the seven leaders of Team Plasma. The Player fights them throughout the game and fights the leader, Ghetsis and then they block the way to N. All the Gym Leaders come and clear the path to N. After the player beats the Elite Four, the player must help Looker find them over Unova and arrest them. Later, in Black and White Versions 2, the player is able to battle three of the Seven Sages: Ghetsis, found in Giant Chasm; Rood, found in Driftveil City leading the old Team Plasma that still follows N; and Zinzolin, who is found in multiple places commanding the new Team Plasma alongside Colress and Ghetsis.
These sages could very possibly be based on the seven deadly sins.
They could also represent the Hindi translation of the Great Bear (star) - Sapta Hrishi
The names of the seven sages (except Ghetsis) resemble colours of the rainbow.
Zinzolin is French for reddish purple.
Gorm is Irish for blue.
Bronius is German for brown.
Giallo is Italian for yellow.
Ryoku is Japanese for emerald green.
Rood is Dutch for red.
The Seven Sages could be based off of the crusaders including Ghetsis because Team Plasma is based off of the medieval times hence King N and that they are knights.
One of the Seven Sages, Zinzolin, is battle-able in Black and White Versions 2. His attire is ironic, with him wearing a winter jacket. This is ironic since it was him who was always found in the Cold Storage (in fact, he had his grunts huddle around for warmth when you find him in there the first time). Seems he was prepared for the cold due to that, as none of the other Team Plasma members are seen wearing any sort of protective attire, even in frozen over places.