First off, which ACOG did you try to unload? I am desperately searching for a used TA11 at the right price... any TA11!
I have a Comp ACOG on a gun with a 6v lite, but have not used it much in reduced lighting, so I dont know how well or not the 6v light and ACOG work together.
My TA31 has a M900, or, a 9v light and I use the high output bulb. I have found that the brighter light does make the difference. What I noticed without the blue filter is that the areas is lit up so well and so brightly that even if the reticle turn black, the dark black reticle against the brightly lit background still allows you to keep track of the reticle.
The blue filter just cuts a fair amount of the light and keeps the reticle red. The blue background and the red reticle provide a good contrast.