[metapost] CMYK colors

[Troy Henderson]

Is there a reason that when the CMYK colorspace support was added to
MetaPost that the colors "cyan", "magenta", "yellow", and "key" (or
"black") were not added as synonyms to (1,0,0,0), (0,1,0,0),
(0,0,1,0), and (0,0,0,1), respectively?  I can understand why "black"
would not be associated with (0,0,0,1) since black is already
synonymous with (0,0,0) in the RGB colorspace, but "key" could be used
in its place.

Thoughts?