A while back I started getting tired of the default Outlook reply colors (yeah, I was bored...).  The font picker under Options/Mail Format/Fonts doesn't let you choose colors outside the standard 16, and I didn't want to use the Stationery option, so some registry hacking was in order.  After a bit of tweaking I found the key:

[HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Common\MailSettings]
"ReplyFontSimple"=hex:3c,00,00,00,0f,00,00,e8,00,00,00,00,c8,00,00,00,3f,c2,72,\
  74,1c,52,45,00,00,20,41,72,69,61,6c,00,00,00,00,00,00,00,00,00,00,00,00,00,\
  01,00,00,00,90,ea,13,00,01,00,00,00,01,00,00,00

The highlighted numbers are the RGB values in hex, so the color I use is #1c5245 - a dark blue/green.  As always, use caution when editing your registry.  If there's an easier way to do this feel free to comment.  (It's been said that something like 90% of the feature requests that the Office team gets are already in the product.)

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The tip of the day is a keyboard shortcut: Alt+F1 toggles the navigation pane in Outlook 2003.  I use the reading pane on the right, and this is perfect for viewing those emails that cause a horizontal scrollbar to appear because they contain an HTML table with a fixed width.