absolute or relative color tables? or ice is always blue

Bill and VisAD-ers:

How do I make a color table or ColorControl so that there
is a connection between a particular color and a particular data
value or a range of data values?

So far as I know a color table in VisAD spans whatever values are displayed.
Two displays of the same parameter (but different max and mins)
have differing colors for the same parameter value; very confusing.

Eventually I want to set up a display so that it knows which colors
to use for which parameter type as well; if I am plotting a budget I want
red for less than zero; if I am plotting temperature I want 
pale blue for less than zero.

Cheers,

Stu Wier

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