Why is it greyed out?

I realized editing the crosshairs was an option after reviewing Necros play and noticing his cross hair was different- but one of the FEW THINGS I want to change just won’t let me do anything with.

I realized editing the crosshairs was an option after reviewing Necros play and noticing his cross hair was different- but one of the FEW THINGS I want to change just won’t let me do anything with.