[GRASSLIST:4770] r.in.tiff: problems

[lawrence moran]

Hi,
 
Thanks to those who helped with my previous query- I'm now getting somewhere!
 
Next I'm trying to bring in some SRTM topographic data. I've used MacDEM to merge 4 degree squares and exported these as a tiff with world file. Using r.in.tiff, I get three bands (.r, .g, .b). However band .r displays as null values, .g and .b display as greyscale. 
 
Any ideas what's going on?
 
Thanks,
 
Lawrence