A little more in depth, a permanent is any card or token in the 'In Play' zone. This includes Lands, Artifacts, Enchantments, Creatures, Planeswalkers, and Tokens.
The color of a permanent is always the same as all of the colors in the card's mana cost unless changed be another card like Illusion, otherwise stated on the card as in Kobolds of Kher Keep and Transguild Courier, or, in the case of tokens, during creation of the token as with Spectral Procession. If a card does not have a mana cost, has no colored mana in its cost, did not have it's color defined on creation, or lost all of it's colors, it is colorless. Oh yea, and a spell with colored mana can be natively colorless the same way a spell with colorless mana can be colored, but so far, only in the case of Ghostfire