I have been using several different laser tools,  I use a laser in a level  (cobalt from lowes to set up my flags and wind-probes.    I have used several different kinds--all red ones--as boresighters.  I too ordered a green one  ( Green Dot Laser Bore Sighter Boresighter Kit .22-.50 Caliber Rifle Scope Hunting     Sold by LMJ-US)

it just arrived today it is significantly brighter than ANY of my red ones.  I have had similar ones that also use the cone/stud with the attachable bore guides for the stud as well as one that is inside a dummy 223 cartridge.  none are perfect but usually they'll get you "on paper" at 100 or 200 yards if the light conditions are right.   Hopefully the green laser will be a little more flexible in terms of ambient light conditions.  and hopefully it won't have as much MOA dispersion at 200 as the red ones.