Black and White
'White' is technically the combination of ALL colors.
'Black' is technically the absence of light.
For most of our purposes in the world of graphic arts and printing black and white are considered colors.
If Black and White are balanced against each other in just the right proportions the results can be historic.
Sometimes You Can Find Miles Between Black and White
Shades of gray are used as colors in all visual media.
Silver as a 'color' involves grays.
Gray occurs in nature and as shadows every where.