The tail light housings of a second generation (2015, 2016, 2017, 2018, 2019 and probably also the face-lifted 2020 model year) GM Chevy Colorado truck each contain two combination brake / rear turn signal light bulbs and a single reverse (back-up) light bulb. Check out my DIY instructions for changing any of the bulbs (with the compatible replacement part numbers) by clicking on the text link or thumbnail image below.
2015-2019 GM Chevrolet Colorado Tail Light Bulbs Replacement Guide
Owners of the similar GMC Canyon, Chevrolet S10 (Argentina & Brazil / Brasil), Holden Colorado (Australia) and the related Isuzu D-Max may also find the DIY instructions to be helpful.