What color is Envelope, The Water Resources Council, Inc., 270 Park Avenue, New York, NY, 1958 ?

Source Crayola® CSS3 CSS4
#688aa6
 
#6699cc
blue gray
#778899
light slate grey
#778899
lightslategrey
#4f4e43
 
#414a4c
outer space
#2f4f4f
dark slate gray
#2f4f4f
darkslategrey