Search online for Kymco Agility Scooter Repair Manual.
Download it. Look thru it for body panel removal info.
You might find something like this:
(If it doesn't show up,) open up seat, remove under-seat box, Remove black panel in front of same (I start prying from the lower front on this.) Remove rear rack. Remove colored body panels, via screws/push-plugs under edges. You should now have access to rear of turn signal lights. (This info good for US spec/original Agility, the Agility City versions are something different!)
Hope it works for you, removing the plastics the first time made me nervous something would crack
, for me it worked out OK.
Good Luck!
Edit: To completely remove the colored body plastics, the seat lock cable should be undone from the latch, pull cable loose from fixing, pivot to release end of cable from latch.