Can't believe I found this on Apple's Support website:

http://docs.info.apple.com/article.html?artnum=866

"Apple does not normally use PMS color charts or Pantone color numbers to designate the platinum color that is now the company standard. Our platinum color number on a coded PMS chart is somewhere between 420 and 421, somewhat closer to 421. (This depends on the age of the chart and the light source used for viewing it."