The only bit darker than 220 (out of 255) is the drop shadow, whose darkest part is close to RGB 180,180,180. For reference, the colour of the frame inside the drop shadow is RGB 240,240,240.
Very subtle shades you have going here. Had to go to my good CRT to view it. Both the Dell and Apple laptops did not give it justice. Good example of using diagonal.
source photo