Calendar Color - Configuring Show As field Color Options

I am wondering if there's a way to configure the Show As field color options when booking a meeting or an appointment. My color show like this:

• Free = White
• Working Elsewhere, Tentative, Busy = Light Purple (with different patterns)
• Out of Office = Deep Purple (maybe maroon-ish)

I'd like to change the Out of Office color - if possible - to say, #ff0000 (aka Red)

I've checked numerous tips and tricks sites, I've played around with the various settings myself within Outlook, but have failed to change that color.

Is this something that  simply can't be done? (I'm guessing it can as it's been set already). 
Or is this something that must be done via a Registry setting? If so, can you please point me to the setting? 

Appreciate any help. 
Thanks,
T4H