While the paint code remains the same, there are different "throws" of metallic silvers. The cars painted by the manufacturer at the beginning of the day will have a very slightly different "throw" than those made of the same color code at the end of the day (due to variances, in temperature, humidity, and paint qualities, etc).

This is why, when you are matching colors and you get chips for your code, there will be between 3 and 8 variances or "throws" of that color. The differences are so, so subtle that some people can't even see the difference when holding the chips in their own hands.

The codes on the chip will indicate variances, for instance WV2 will have a "prime" color, which is the standard, and variances with labels like "WV2 (//L)" meaning "two throws lighter" or "WV2 (D)" meaning "one throw darker."

The differences that the OP is obviously noticing is the szhizophrenic nature of Silverstone. Due to the heavy metalic flake, it looks very different depending upon angle, lighting, and the surrounding colors.

In some parking lots mine looks almost bronze, and in other lights it looks like a metallic blue. This is why it is one of my most favorite colors. Chrome Silver tends to change colors a lot too, btw.