This has actually been bugging me for years. I don't even know why VO does this, but it forces your system (in OSX anyway) to use a specific color setting for the monitor.

Now this really wouldn't be a problem if all I ever did was play the game and nothing else. Unfortunately I'm an artist of sorts and my work involves my computer and a burning need for accurate colour. Therefore, I can't have VO on in the background and work at the same time, which I need to do from time to time (or all the time, productivity be damned!)

Umm. That's odd. VO changes your color calibration settings? I can have Ray look into this as a low-priority thing. It may be an OS-level issue though, like OpenGL apps causing some sort of driver calibration change. But, that's a bit surprising for the Mac platform, where color calibration is considered so critical.

[EDIT]: writing a ticket for it now. What specific version of OS X are you running? Do you have one of the Cinema monitors, or built-in (iMac), etc? What kind of video chipset? Thanks.

Ah yes, it does that for me. When I launch Vendetta my screen takes on a blue-ish hue (Vendetta looks normal). This is only noticeable in windowed mode, of course.
OS 10.5.5
iMac G5 2GHz, ATI Radeon 9600 (128MB)
17" built-in monitor (1440x900)
22" Dell external monitor (1680x1050)

When VO is launched, the monitor color profile changes to an extremely cold tinted color, and restores to normal upon quit.
I'm using Mac OS 10.5.4, with a built-in display on the MBP 2.4 GHz (Santa Rosa?). GeForce 8600M GT with 256 VRAM.

I've noticed it for years too, I just figured it's a thing games do. Might be worth noting that WoW has two options for gamma, first is game set with a slider, the other is "Use Desktop Color."

I'm running an Intel Macbook Pro 2.4 running 10.5.4, but it really has been present since I started out on my old PowerPC dual 2.0 G5 running 10.(3?) and a Viewsonic Monitor.... I'll get more specific details on my present rig for you in a bit...

VO has been doing this for me under window mode in OSX since I started playing way back in 2002, on the following machines:

2002 - 2006
15" iMac G4 800MHz ("iLamp" model)
10.2.x to 10.4.x
GeForce2 MX 32MB
15" built-in screen (1024x768)
No external display

2003 - Present:
iBook G4 1.2GHz
10.3.x to 10.4.x
ATI Radeon Mobility w/ 32MB (don't remember the exact card)
No external display
14" built-in screen (1024x768)

2006 - Present:
15" MacBook Pro, 2.33GHz Core 2 Duo
10.4.x to 10.5.x
ATI Radeon X1600 256MB
15.4" built-in screen (1440x900)
22" Acer X223w external monitor (1680x1050)

VO isn't the only game that does this...

I'd wager a megacredit that this is due to some OGL quirkiness >_>