DPA VM Option - what does it monitor?

Our DBA team uses both DPA and SQL Sentry to monitor all things database.  We had an issue kind of creep up that we noticed in DPA and I was asked the question "What does DPA use for metrics in VMWare?"  What does Disk Red mean?

I was trying to find the answer on Solarwinds site but got stuck in the Buy Me Now loop.  Is there a document or information on what Disk red means in DPA? We also run the VM Option in DPA and I was wondering what that uses/looks at in VMWare. 

I usually just update DPA and let the DBA team roll with the software.