The out of the box "Datacenter Overview" dashboard view is using a health status indicator which splits resources into four possible states:
- above threshold (red)
- above guidelines (yellow)
- within range (green)
- under utilized (light blue)
I think this approach is very useful, since avoiding under utilization is one of the goals of capacity management, and therefore it should be extended also to custom dashboards, specifically to table portlets, by giving to the user the option of defining also the under utilization threshold.
Currently the table portlets allow only to configure two thresholds, i.e. they allow to define only red-yellow-green intervals (which, indeed, is good for most cases and in my opinion should remain the default choice).