Here is the full list of all 22 ChromaGun achievements.
Finish Chapter 1.
Open a door by activating a trigger.
Try jumping... and fail.
Shoot a WorkerDroid.
Find the hidden cake we actually have, as opposed to that other game that doesn't have a cake.
Mix a color. It's not that hard, really.
Try painting a brown WokerDroid and realize how pointless that was.
Fire 100 shots.
Grill a WorkerDroid on a Deadly Electrified Maintenance Tile.
Grill 100 WorkerDroids on Deadly Maintenance Tiles.
Finish Chapter 2.
Finish Chapter 3.
Finish Chapter 4.
Finish Chapter 5.
Finish Chapter 6.
Finish Chapter 7.
Finish Chapter 8.
Solve a chamber in chapter 7 without firing a single shot.
Try jumping over a Deadly Electrified Maintenance Tile... and fail horribly.
Simply walk onto the Deadly Electrified Maintenance tile in Chamber 3-1.
Get killed by a WorkerDroid.
Rescue the WorkerDroid in Chamber 5-2.