Pink feathers are pornographic. Cream is the color of a used up feather. Only blue, black and pink feathers go cream. Their makers want the users coming back for more. Silver feathers are for the system operators, the people who make the feathers and mix the dreams.
Yellow feathers are the most dangerous.
They are Knowledge Feathers. But if you die in a yellow Vurt, you die in real life. Like a vast computer game, there are various levels to all these realities. The master of ceremonies in all levels is a character called the Game Cat, who is part instructor, part oracle and part sphinx, and whose enigmatic sayings are quoted throughout the novel. Sometimes things and people disappear into the game and are exchanged for other things.