MongoDB Instance Summary dashboard: Ensure colors for ReplSet status matches those in MongoDB ReplSet Summary dashboard for better consistency

Dashboard: "MongoDB Instance Summary" 
Element: "ReplSet states" 

Colors of elements are not bind to statuses. So Seconadry state can be shown in green and Primary in yellow color.

It's required to set Primary - green, Secondary - yellow as it's done on "MongoDB ReplSet Summary" dashboard.