RGB "codes" don't really say anything about the actual
color, which depends on the device and its calibration.
It is a very complex matter indeed to get a reasonably
consistent rendering of colors between various printers
and displays for the same image data.
In the world of manufacturing and graphic arts, the
Pantone system seems to be the most widely used.
See:
http://en.wikipedia.org/wiki/Pantone
But no, I don't know the Pantone numbers for the DEC
panels, and based on Will's comments, I doubt there ever
was an official one. I did see some discussion of
cabinet colors at one point that indicated that the
official standard was a particular paint manufacturer's
part number.
--Bill