Color name not defined?

["A. Michael Salem" <michael.salem@stanford.edu>]

Hi,

I am having a problem with color names not being defined. Here is an 
example:

>xterm -bg black
Warning: Color name "black" is not defined

I do have the file //usr/lib/X11/rgb.txt/ with "black" defined.
And when i run >showrgb it prints these values...

Any idea whats going on?