Might depend on what colour your truck is. If they sold you colour match for a colour the factory doesn't supply, then they planned on painting them.
Either way, the dealer installs them.
A capable body shop should be able to paint them without peeling if it's not a factory supported colour.
SF6 LPO, Body color wheel arch moldings, (dealer-installed)
SLE - Requires exterior paint (GAN) Quicksilver Metallic, (GAZ) Summit White, (GBA) Onyx Black, (GJI) Dark Sky Metallic or (GCI) Carbon Black Metallic. Not available with (ZW9) pickup bed delete, (VQK) front and rear Black molded splash guards, LPO or (PDH) GMC Interior Protection Package, LPO.
SLT - Requires exterior paint (GAN) Quicksilver Metallic, (GAZ) Summit White, (G1W) White Frost Tricoat, (GBA) Onyx Black, (GJI) Dark Sky Metallic or (GCI) Carbon Black Metallic. Not available with (ZW9) pickup bed delete, (VQK) front and rear Black molded splash guards, LPO or (PDH) GMC Interior Protection Package, LPO.
AT4 - Requires exterior paint (GAN) Quicksilver Metallic, (GAZ) Summit White, (GBA) Onyx Black, (GJI) Dark Sky Metallic or (GCI) Carbon Black Metallic. Not available with (VQK) front and rear Black molded splash guards, LPO or (PDH) GMC Interior Protection Package, LPO.
Denali - Requires exterior paint (GAN) Quicksilver Metallic, (GAZ) Summit White, (G1W) White Frost Tricoat, (GBA) Onyx Black, (GJI) Dark Sky Metallic or (GCI) Carbon Black Metallic. Not available with (VQK) front and rear Black molded splash guards, LPO or (PDH) GMC Interior Protection Package, LPO.