RECOVERED alerts red->yellow

[Alan Sparks <asparks (at) doublesparks.net>]

I have the following settings in my hobbitserver.cfg:
ALERTCOLORS="red,yellow,purple"
OKCOLORS="green,blue,clear"

I have the following rule in my hobbit-alerts.cfg:
SERVICE=disk COLOR=red
   MAIL asparks (at) photobucket.com RECOVERED

I get an alert when disk space goes critical (red).  However:
* when the status goes from red->green, I get a recovery alert;
* when the status goes red->yellow->green, I get NO recovery alert.

I've read the sections on ALERTCOLORS and OKCOLORS.  It does work better 
when I remove yellow from the list.  But I need to sometimes alert on 
yellow status, so this is not really an option.

What have I done wrong?  Thanks in advance.
-Alan