Click on the image below to see it in action (because my post does not allow it to be dynamically displayed).
3 Dimensions are:
definition of groups that share the same kind of color
each square with it's area
each square is more or less dark and more or less saturated
This is something that you I use to display a status of issues on a bunch of projects. For instance we develop several keyboards and mice at the same time.
The yellow group of color could group all keyboard projects.
square area is proportional to thetotalnumber of bugs for this project
square darkness and saturation/alpha is proportional to the number ofopenbugs for this project