back to the OP's original question, check out the:
IR Cannon w/Adjustable Focus
the adjustable focus will work very well with a Varifocal Starlight; many of the images I posted up in the review show that it basically eliminates all noise and gives you a very detailed image even at high shutter speeds.. I installed the IR Cannons to help w/the 4MP Camera's poor capabilities; but I will keep them long after I replace all these cameras w/Starlight equivalents..
I would not run it in color mode at night unless its an alternate angle or if you just had badass visible dusk2dawn lighting that allowed a decent shutter speed.. Visible lighting is not always better, if the area was otherwise completely dark it really slows people down when they cant see shit.. dont provide em light to work with if you can help it, if you force em to break out there own flashlight then they are alot less discrete and someone is likely to notice it.. motion activated lights havent scared off anyone in decades, its not like they have never encountered them before and actually think someone is physically watching em.. that ship sailed long ago, there is zero psychological advantage to having the lights turn on since they will do so all the time even if nobody is out there to trigger em.
Disabling the onboard IR and using external IR does have advantages if you can cope with the aesthetics of it all.. if your watching a parking area and you move the source far enough away from the lens none of the reflectors will flare up for example.. but doing all this to get better motion detection results is not the path a wise man will travel.. You add more lighting to improve quality and reduce noise, the rest is just icing on the cake.
Any camera, starlight or naught will benefit from additional lighting Visible or 850nm IR.. the difference was night/day w/my non-starlight cameras and a bit less so with my starlight cameras but still worth the performance increase.