image processing- i.composite?

[T.W.CHARNOCK]

Hi

I'm trying to use the GRASS image processing facilities on some 
landsat data.  But I am unable to produce a satisifactory composite 
image.  Have have tried using i.composite and i.colors.  Both the 
images produced are far too dark with only the clouds showing as 
white patches.  As both of these operations start I get the the 
message:
WARNING: histogram file missing (or something like)

i.colors should be interactive but it would operate for me other than to 
resize the image and swap bands.

Any idea what I'm doing wrong

cheers

Tom Charnock               
Dept Civil Engineering     
Aston University          
Birmingham UK                           
charnotw at aston.ac.uk