Originally Posted by richerich
My player only has a yellow output
Then that's the composite output and it should route to a yellow input
on your TV with just one lead (two others red/white for the audio). You can get a three lead bundle which includes the two audio if you like. Don't plug anything into the red/green/blue TV inputs.
Probably like jkkyler described - you were running the yellow to one of the red/green/blue inputs on your TV.
Try yellow to yellow and let us know what happens. If that is already the case, then something else is going on which is producing the B&W picture.