[NTG-context] color question

[jbf]

I have a very basic question about color use that someone will be able 
to answer easily. The background to the question is that (i) I am 
completely new to this scene of commercially[offset] print-ready 
material as distinct from what is required on screen (ii) I am using Mk 
IV (iii) I need spot colors set up for cmyk, and for now I need shades 
between black and white (e.g. light gray) for a simple design feature.

My question is this: is the use of color keywords sufficient? Or in 
other words, have predefined color names like lighgray already been 
defined in, say cmyk terms behind the scenes, or must I instead 
\definecolor[lightgray][c=10,m=7,y=5,k=0],   (or perhaps 
\definespotcolor with those dimensions, or do I need both)?

Julian