IR Colour Vision
As in the previous posts I hope that sense prevails on CVD and night flying with an IR. I too have problems between white and green when doing a lantern test and hence have the daytime only restriction on my CAA PPL.
There is no restriction on my FAA PPL which includes a night rating and IR because in the testing it has not been found to be relevant. However I know from experience that, for me, it is difficult to spot an airfield at distance by the green flashing beacon, when it is located amongst thousands of other lights in or near a city.
The only reason I can see that affecting an instrument flight is if the pilot should choose, or maybe be forced by equipment failure, to change during the flight from IFR to VFR. Making a visual approach under IFR is only done when the airfield is in sight anyway.
I would not want to invest time and money in an IR with a daytime restriction either.