I was interested to see a "Sample Average Color" GIMP script appear at the repository. The image below is a rundown of how it works. To install it in Linux, drop the .scm file in your ~/.gimp-2.6/scripts folder.
This script may be helpful to some; people who have taken my computer graphics classes may recall that there is a similar, and quite comprehensive tool online at colr.org. More tools are listed at the color tools section of the Art 86 website.
Eliteness note: Yes, I taught Photoshop and other Adobe products to college students, and I enjoyed it. And I do use GIMP too! Don't be afraid to add new tools to your arsenal - learn their strengths and weaknesses. GIMP is especially handy now that my creative workflow has gone entirely Linux-based due to buggy software. There are some really nice third-party plug-ins and scripts available for GIMP, too.