How come some stats are green and others are blue in Configured Collections views?

Stats marked green are actively being polled by WM.  Stats in blue are available to be polled, but have to be enabled first.  This is accomplished by double clicking the stat and selecting the "Active" radio button.  

By default only stats considered as key performance indicators (KPIs) are polled.  In some devices there are literally hundreds of stats available.  While useful in some instances, leaving all stats enabled by default would result in a tremendous amount of polling traffic which would cause the overall network to degrade.