Taking Advantage of the Camera

I should have thought of this earlier. The IR light coming through and the fact that my replacement for the IR-cut filter does not have the same visible tint was throwing the white balance off. I forgot the camera has a manual white balance control. Setting off a white piece paper I can wholly compensate for the magenta shift in colour in-camera:

IR+Visible, correctly white-balanced.

IR only, correctly white-balanced.