Pure Metal Silver

Pure Metal Silver is the most expensive paint option that was offered by BMW ~ € 8k / $ 10k. It's currently no longer available.

It was first offered on the F10 M5, there even was a "Pure Metal Silver Edition" with 50 units going to North America and 20 to South Africa.

To achieve this deep silver effect, the chassis is first sprayed with a base coat of Glacier Silver Metallic before the actual Pure Metal Silver coat(s) are applied.
Here's how BMW describes the color: With the BMW Individual paintwork Pure Metal Silver, the body takes on a deep, brilliant lustre. This unique metallic gleam is down to the combination of a special-effect pigment with a water-based paint system. The addition of ultra-thin aluminium flakes guarantees a uniform and gleaming surface. Depending on the angle of view, these flakes create a light-dark contrast and accentuate the surfaces of the body. This paintwork showcases the model’s lines and contours to even better effect and adds striking touches to the vehicle’s design.