Just wanna know. Because I was testing that Keystone ballast in my fixture and it fits and works perfectly, but since the stupid wires of the lampholders won't come out, since it was pressed in for some reason. But after testing the ballast I put back the orginal ballast and I wanna know if putting wire nuts on the blue and red side of the ballast is safe?

Why not? Assume they are used how they should be...