When you tell your readers what colour something is you're usually telling them what they already know or else something unimportant. But once in a while colour does matter. For instance:
2. It can give what you're describing importance. Most stones are grey. So if you described a stone as being white or black you would draw the readers' attention to it and make the stone suddenly important.
3. It foreshadows future events. If one of the doors on the street is painted black, you may be foreshadowing that there will be a death in this house later in the story.
4. It reveals character. Why does someone in your story wear a purple tie? Perhaps to show that he's eccentric, wants attention, or simply doesn't care what others think of his fashion sense.
Most colours have one or two meanings that are familiar to everyone. You would probably want to stick to the more well-known meanings so that you don't have to do any explaining to get the point across.
Context is everything. If you describe a dead tree as being white, readers will get the idea of death. An angel in a white gown? Probably innocence. (Unless it's the angel of death...but you'll be able to make that clear.)
It's not always the exclusive property of the villain, though. On a good guy black can simply mean he's someone who's serious about what he does, or someone who's definitely a force to be reckoned with.
Red can stand for danger, passion, desire, bravery, and love. In China it also represents wealth and good luck. It makes people think of roses, which stand for love; poppies, which stand for both memory and forgetfulness (confusing, isn't it?); blood, which stands for life; and fire, which stands for passion and/or desire. Use context to let readers know what meaning you're trying to convey.
On the other hand, yellow can stand for hazard (yellow road signs) and cowardice (calling someone "yellow").
Grey, because it's the colour of ashes, also represents repentance--an important element in many stories.