Chevrolet 2006 Colorado Owner's Manual page 56

Extended Cab — Rear Seat
For regular and extended cab models without rear seats,
there is a top tether anchor located behind a removable
cover on the back wall behind the right front passenger
seat. You may have to pull the seatback forward to
access the anchor.
1-50
Do not secure a child restraint in the right front
passenger's position of a vehicle that has rear seats
if a national or local law requires that the top tether be
attached, or if the instructions that come with the child
restraint say that the top tether must be attached.
There is no place to attach the top tether in this position.
Accident statistics show that children are safer if they
are restrained in the rear rather than the front seat.
See Where to Put the Restraint on page 1-44 for
additional information.