I was looking out in my back yard this evening, and observing the warm and cool relationships caused by the sunlight and cast shadows. I noticed a piece of grey metal that had a yellow color to it because of the sun there was also a nice blue cast shadow falling across it. Then I started wondering this:

If the color of an object is determined by the colors in light that it doesn't absorb (or the reflected color), why does the visible color of a light affect the color of an object?

To clarify: If I have a grey object being hit with evening sunlight, why does the yellow of the evening sun dominate the overall color of the object? Shouldnít the object absorb the excess color and remain grey? Iím obviously missing something here.