In our "Symbols and Tropes" section, we talk about how light always represents good and darkness always represents evil in The Lord Of The Rings trilogy. When we see Gandalf in his shiny new White Wizard getup, we see in him a reflection of hope and a kind of righteous power that can banish the shadows back to the dark corners of the earth.
But wait a minute. Saruman is also a White Wizard. What gives?
Well, Saruman used to be on the side of the free beings of Middle-earth. He was just like Gandalf, a Maiar sent down to the world to help out elves and men (and hobbits, of course). But Saruman was corrupted by his hunger for power and knowledge. In fact, in the books he renamed himself Saruman of Many Colors, ditching the whole white/light/goodness thing and embracing his… true colors.
While in the books, Saruman was bent on gaining the Ring for himself and betraying Sauron, in the movies he's portrayed as Sauron's puppet, someone ensnared by his trap through the Palantír:
SARUMAN: The world is changing. Who now has the strength to stand against the armies of Isengard and Mordor? To stand against the might of Sauron and Saruman, and the union of the two towers? Together, my Lord Sauron, we shall rule this Middle-earth.
As Sauron wills it, Saruman builds a giant horde of orcs to crush Rohan. But he doesn't create just any orcs; he makes a fresh batch of uruk-hai. These guys are some messed up hybrids of dead elves and men. Saruman is seriously screwing with mother nature (which is underlined by him going all industrial revolution and burning down Fangorn Forest).
But all of Saruman's power and wisdom can't save him from the angry river and angrier trees. We hope he's been practicing his levitation spells, or things for Mr. S. are about to get very wet.