Grass Tutorial

I'm new to GRASS and am in the process of familiarizing myself with GIS.
I have heard the rumor that there is a good GRASS tutorial out there
somewhere and I am wondering if anyone knows where it might be found.

I am familiar with the way GRASS operates but I am having trouble getting
my data to display in GRASS. When I import my raster files into GRASS
and try to dislay them I get the error "color file not found". Is this
because I need an entire database? Any help that you can give me would
be GREATLY appreciated. Thanks in advance for your help.

                              Shaun Poulton
                              National Marine Fisheries Service
                              spoulton@solidsparc.ssp.nmfs.gov
                              (301)713-2372