There are good techical reasons for us not handling it, the biggest of which is that the display that is connected to the VM isn't a real monitor; as far as the guest is concerned it has a perfect display (i.e. It's exactly a gamma 2.2 display) there are also issues with VM portability: if you move the VM to another machine the display calibration would need to change to remain correct. It's really up to the host to correctly handle the colour calibration. For normal desktop machines we could probably do just as well as the host would manage, but for systems with workstation class graphics, we're better off letting the host handle it those machines often have hardware dedicated to properly handling the colour calibration (fine-grained gamma LUTs for analog displays, 10 bit per channel outputs for digital, or even just self-calibrated displays). Fusion only operates with 8 bit colour (OS X doesn't have any provisions for wider-bit colour spaces as far as I know) so we can only make fairly coarse adjustments on the same order as the difference between two adjacent colour levels.
I understand that you only want to get access to the property sheet, but doing so would cause colour-aware guest applications to incorrectly think they were on a calibrated system and change their behaviours.