We paint all our HFT targets pillar box red with bright yellow kills. We take the view that it's a shooting sport not a test of your eyesight.
On our FT course we paint the freestyle targets black with yellow kills, and the positionals are yellow with black kills as a reminder to those who somehow miss the K or S which is displayed by the target and also on the scorecard.
None of our targets are in dark conditions. We do play little tricks though, like painting a black backboard placed immediately behind a black target, and some of the animal targets are decorated with flashes of colour, like the white scuts on the rabbits.