Have a look at DCS 34-80-20 PFD Indications.
"In case of RA detection, the vertical speed needle that is normally green, becomes white." (Presumably so you can see it against the green background).
The inhibitions are listed in DSC 34-80-10 Advisory inhibitions.
It looks like something was inhibited but the needle displayed turned white anyway. (I'm surmising at this point).