I would assume he is ordering an after market kit Danny some will supply them pre coloured
o/p Yes 2 coloured and 2 black for the bumper insert the bumper is marked on the backside for drilling them (least that way you will get them even without spending an hour with a tape measure and pencil)
Why not... its his car, he might have mobility problems/ just be plain lazy or just like tinkering with his car
That said the system i fitted on my last GP saved me at least twice from backing into something immovable ( and was invisible so no one knew i had parking sensors fitted )
lamp post in the corner of a parking bay hidden ever so well by the rear pillar and the fact it wasn't working
and a very high curb in a very dark wet country pub car park..... The system more than paid for itself in those 2 events in the lack of need to visit the body shop...
(the single reversing light just isn't enough to see by in those sort of circumstances IMO)