If you hover over each of those icons, it shows you what it's for.
Gray is story points (or whatever you measure by) not started
Blue is measurement in progress
Green is measurement done.
See my example below. When you hover it shows total story points or whatever you are measuring by. I use story points.
I am having this exact same issue. We just noticed it this morning. Our audit log indicates nothing that would cause this (just general user management). Our build info is below:
|Build Date||Wed Oct 26 00:00:00 EDT 2016|
|Last Upgrade||26/Oct/16 1:41 AM (v1000.456.2#100016)|