The two paragraphs are saying the same thing; I think Pinker is making a bit of a grandiose philosophical statement in the meaning of "the world as it is", but it makes sense if we give that the narrow meaning he's actually using: the "world as it is", the color of an object, refers to how that object reflects light. Not the spectrum of light emitted, which changes by the ambient light available, but how the object changes the ambient light spectrum to reflect just part of it.
The distinction he's making is in the difference between perception and the actual signal entering the eye; alternatively, think of that signal as what one pixel from a digital camera would register. Perception will be constant ("match the world as it is"), while the camera pixels would register something very different for the same object in different contexts.
A white snowball reflects light the same whether it's inside a candlelit room or out in the bright sun, but because the light source is different you will receive a completely different spectrum and intensity of light at the eye (or camera) in those two settings. However, the perception of the snowball being white stays the same. It stays the same because you aren't directly reading the count of photons of different wavelengths coming off the snowball to decide it's white, you're making comparisons with all the other light coming off all the other objects in the room to determine how much ambient light there is, and based on that, which wavelengths each object in the room must be reflecting ("the world as it is").
The TV example is the same, just from a different perspective. You're perceptually making the same "ambient light" corrections as the candlelight/sunlight distinction, except in this case for the emitted light of the TV. If, say, the TV is showing a picture of a car driving down an asphalt road, the asphalt is black and you perceive it as black even if there is actually the pale greenish gray light entering the eye.