What Ford meant by this is not hard to understand. He meant that he was making the car in one color only. What is more interesting is why he said that and why he was able to say it.
Ford was able to get people to buy a car that came in one color only because it was a good car at a superior price. Ford was basing his strategy on the idea that a car that was affordable to the masses would be competitive on its own, regardless of whether it came in colors or had other of what he called "trimmings."
So this is a statement of the power of price. It is a statement of how important it is to move a product from a price point where it is available only to select consumers to a point where it is affordable to the masses.