While going from oyster to any other color would be cheap (by way of repainting), going from charcoal to any other color besides a black will be very, very expensive since you won't be able to repaint.
If you want a consistent look, you'll need to change out the center console, seats, door trim, backseat trim band, instrument surround, and even the rear lid trim (if it's not black). It'll run you about $6300.
If you just want the seats, door trims, center console trim, and instrument surround , it'll still be about $5500. About the same price as if you were to have it professionally reupholstered. Except that you may be able to cut your cost down to at least half--if you can find buyers for the original pieces.