Glow in the dark balls, that will be fun.
Our dog (wife's) is a black lab, you cannot see him when its dark out.
I bought a flashing collar, that rotates neon green around it.
It is funny watching him run thru the yard, by the road, passing cars do not know what to think. Sometimes slamming on their brakes and swearing.
One of mine is an all black GSD, the other three are black and red. I've got pretty good lighting out back, so I can see em, but once I light up the balls, I get to see green lights (the balls) running all over!