Tim,
It seems nearly nothing is the same with the GMC's! But I love them. The color combo's were dark green/light green and dark blue/light blue. Might have been other but I'm going off failing memory here. The patterns are not the same as Chevy either.
Take a look at this link:
http://community.webshots.com/photo/82943810/94661952dopUrk The pattern is solid for the dark green and vertical lines for the light green. The blues use the same patterns.
I'M GOING TO REPOST THIS IN THE INTERIORS SECTION.