Well impulses have been good enough for top teams like the ton-ton, ducklings e.t.c for years with reflective eyes, make sure they are clean and then just use light coloured paint, i've used dark colours with mine and the only ones i had any trouble with was some crappy site paint in a very dark green colour, but everything else even dark purple seems fine. Most manufacturers make light coloured paint anyway so just stick to a good, light colour and you shouldnt have any trouble.
Also, what pressure are you running at?, chopping isnt always a case of bad vision.