We tried a few different colour combinations in the past but the most popular was the Yellow Line paint with Fluorescent orange kills.
As you know we used them for our National so will leave it up to you whether it was the right combination.
The kills do still tend to show up even when the orange is shot off.
I don't know how you cater for people who have colour blindness as it can involve not seeing different colours.
My own view is that the target and kill should be visible as it's not a test of equipment but of shooting ability.