Viserys I, and the question of who comes after

A kind, weak, well-meaning king inherits a realm at peace and spends his reign avoiding the only decision that matters. He names his daughter Rhaenyra his heir and has the lords swear to her; then he takes a second wife, Alicent Hightower, and has sons. Everyone swears again and quietly makes other plans. Every drop of blood in the Dance is spilled out of this one unresolved sentence.

The fuller tale

Viserys I inherited the realm at its wealthiest and most peaceful and had, by every account, no talent for anything except being liked. He was generous, easily led, and constitutionally unable to make a decision that would upset somebody in the room. For twenty-six years that was almost enough.

His wife died in childbed after he chose, on a maester's advice and his own hope of a son, a delivery she did not survive. He named their daughter Rhaenyra his heir and made every lord in the realm swear to her ÔÇö the first time a woman had been named to the Iron Throne. Then he married Alicent Hightower and had sons, and never once said out loud what that meant for the oath he had made everyone swear.

So the court split into people who had sworn and people who could count, and both halves waited politely for twenty years while the king avoided the subject. The Great Council of 101 had already ruled that sons come before daughters. The king's own oath said otherwise. Nobody was going to raise it while he lived, and the moment he died everybody did.

Greens and blacks

The names come from a tourney gown. Alicent Hightower wore green, Rhaenyra wore Targaryen black, and a court that could not discuss the succession discussed dresses instead. That is the whole political culture of Viserys's reign in one image: an argument about the throne conducted entirely in colours because the alternative was saying it plainly.

By the end the greens held the capital, the treasury and the Hightowers; the blacks held Dragonstone, the North, the Vale and the riverlands, and rather more dragons. Everyone had sworn the same oath and everyone knew exactly which half of it they meant.

Elsewhere in the wiki

 See the world as it stood in 103 AC 

What became of it ÔÇö if an ending is written, it is here. Spoilers.

The chronicle records no ending here ÔÇö or none the maesters have set down.